A Scientific History of Oysters in Chesapeake Bay

December 30, 2016/0 Comments/in Conservation, Ocean News /by a.anstett

By Nicole Suren, SRC intern

Oysters are not only a preferred dish of much of the human population, but they are also very important parts of the ecosystems they inhabit. As ecosystem engineers, or organisms that significantly modify their habitat, they do not just participate in the habitat they settle in but improve it by filtering large volumes of water and forming reefs that other organisms can use as shelter. Unfortunately, the estuary systems that they prefer have been in steep decline for some time due to negative effects of human activity, and scientists are currently attempting to quantify how much these ecosystems have declined by examining the average sizes of oyster populations over time. Here, Rick et al. (2016) focused on Chesapeake Bay in the northeastern United States.

Change in oyster size over time

There is an important relationship between the size of the oysters and how healthy their populations are. Generally speaking, larger average oyster size correlates with a healthier and more abundant oyster population. With this in mind, scientists examined fossilized oysters ranging from 1,500-3,000 years ago, oysters from Native American archaeological sites, and modern oysters to see how the introduction of humans and later new fishing technologies would affect the oyster populations. They found that the prehistoric oysters were the largest, and that the introduction of harvesting by Native American populations did not affect the average size of the oysters. However, the introduction of new fishing technology resulted in an increase in oyster size, but this then decreased to a much smaller average size than the prehistoric samples today.

Measurements of Chesapeake Bay oysters taken by NOAA

What do these changes mean?

Several things about these results are important. First, the increase in oyster size upon the advent of new fishing technology can be attributed to people having access to parts of the oyster population that they had not had access to previously. The Native Americans were believed to harvest oysters by hand, so this would have limited them to slightly smaller oysters in shallow waters. In contrast, new fishing techniques such as trawling would have harvested the larger oysters in deeper waters, so the size increase is likely due to a difference in sample areas between the two time periods. Second, since there was no size difference between the oyster populations before and after Native American settlement in Chesapeake Bay, it can be concluded that the Native American oyster fishery was very sustainable. This is hypothesized to be due to their aforementioned harvesting methods, low population density, broad-spectrum diets (that are not completely dependent on oysters), and lack of a significant oyster trade.

Implications for current management

While it would be impossible to fully emulate the sustainability of the Native Americans of that time, we can use the same principles to modify our own activities to make the modern oyster fishery more sustainable. For example, fishing limits on larger oysters in deeper waters, decreased harvests of all oysters, and restoration techniques can be implemented, all of which mirror Native American sustainability strategies in a modern world. The implications of this study show that science is deeply rooted in cultural phenomena, and can incorporate the best of culture and sustainability to better the planet.

Reference
Rick TC, Reeder-Myers LA, Hofman CA et al. (2016) Millennial-scale sustainability of the Chesapeake Bay Native American oyster fishery. Proceedings of the National Academy of Sciences, 113, 6568–6573.

Age-specific foraging performance and reproduction in tool-using wild bottlenose dolphins

December 26, 2016/0 Comments/in Conservation, Ocean News /by a.anstett

By Elana Rusnak, SRC Intern

Foraging (searching for food) is a skill that animals use to provide energy for survival, growth, and reproduction. In many animals, these skills are fully developed before reproductive age, maximizing the energy put into reproduction when sexual maturity is reached. However, female bottlenose dolphins (Tursiops aduncus) in Shark Bay, Western Australia, learn a unique foraging behavior from their mothers during development, yet continue to hone their skills long after reaching sexual maturity (at around 10 years). This complex foraging behavior includes the use of sponges as tools; the dolphin will forage for a sponge and then “wear” it on their beaks while searching for prey on the seafloor (the benthic zone). The sponge provides protection from sharp rock and shell debris, and allows “spongers” access to a unique food source. Other “non-sponger” dolphins eat fish and other prey in the water column, otherwise known as the pelagic zone. Sponge foraging (sponging) is a complex skill that takes years to develop. Researchers question why such an important skill would not be developed fully before reproductive age.

A female bottlenose dolphin with a marine sponge tool in Shark Bay, Western Australia.

A study published by Patterson et al. in 2016 attempts to explore age-related changes in foraging performance. They examined three aspects of foraging efficiency: the ratio of time spent acquiring sponges to time spent foraging, the time spent foraging per tool (sponge), and the time spent traveling per tool. Their hypothesis estimated that maximum efficiency should result from shorter times acquiring the tool and longer times spent using them. They then examined how age-related changes in foraging performance relate to changes in female reproduction.

The data was collected between 1989 and 2012 and covered roughly 1800 individuals. The three stages of behavior (acquiring sponge, using sponge, travelling with sponge) were classified by the researchers and observed in the wild. Analysis included various statistical tests that modeled the three variables and percent of the population that was reproductively mature against age. It was found that sponge-acquiring behavior makes up a small percentage of an individual’s activity budget (as predicted before the study). As can be seen in Figure 2, until the age of 23.72 years, dolphins gradually learned to spend less time acquiring the sponge and more time using it (a). Until the age of 19.50 years, the time spent foraging per tool gradually increased and then remained stable (b). The model also shows that there was a gradual increase in the time spent traveling per tool as age increased up to 23.34 years of age (c). Finally, the model showed that peak foraging ability improved until roughly midlife (20-25 years), which is well after the onset of sexual maturity. This can be seen by comparing (a), (b), and (c) with (d), which shows age vs. percent of the population at different stages of reproduction.

Age specific foraging and lactation. This shows the relationship between age and the three studied variables, as well as its relationship with reproductively active females.

What did the researchers conclude?

Overall, the data suggest that dolphins continue to improve performance in their tool-use foraging techniques long after they reach sexual and physical maturity. Females increased their foraging efficiency with age by decreasing acquisition time and increasing foraging time. By midlife, it can be concluded that they have learnt how to find the most ideal sponge for foraging, as well as figured out the best way to use it in order to avoid needing replacement. They also learn that reusing a good tool is important, and therefore are more willing to travel with it to avoid needing to find a replacement.

The most important conclusion taken from the data is that while dolphins reach sexual maturity at around 10 years of age, their peak reproductive age coincides with the peak foraging ability (20-25 years of age). It may be that it is advantageous for an individual to reach sexual maturity as soon as their foraging skills are good enough, and then continue to improve efficiency with age in order to increase reproduction. This behavior is seen in other animals, such as chimpanzees, capuchin monkeys, and sea otters. This study proves that we should not be surprised that foraging expertise after reaching adulthood has positive fitness consequences, and allows for higher rates of reproduction.

Reference

Patterson, E. M., Krzyszczyk, E., Mann, J. (2016). Age-specific foraging performance and reproduction in tool-using wild bottlenose dolphins. Behavioral Ecology, 401-410. Retrieved October 20, 2016.

A coming boom in commercial shipping? The potential for rapid growth of noise from commercial ships by 2030

December 23, 2016/0 Comments/in Conservation, Ocean News /by a.anstett

By Josh Ratay, SRC intern

A coming boom in commercial shipping? The potential for rapid growth of noise from commercial ships by 2030 by Kaplan and Solomon is a new study examining potential increases in oceanic noise between 2016 and 2030. Reduction of anthropogenic (human-caused) sounds from commercial shipping has long been recognized as important due to possible impacts on marine life (see https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4626970/). However, previous studies have been limited in scope to just a few coastal areas, and have had limited success at showing the effects of noise across the whole ocean.

Increased noise from commercial shipping can have negative effects on marine animals, particularly those sensitive to sound. Photo from nefsc.noaa.gov.

Here, Kaplan and Solomon combined existing data on commercial fleets with projections of future growth to estimate worldwide shipment and noise levels between now and 2030. The study focused on three classes of ships: container ships, oil tankers, and bulk carriers. The projections suggest a doubling of container and bulk ships in the next 15 years, contributing to an expected 87% increase in sources of marine noise based on ship quantity alone. However, the actual increase is likely to be greater than 87% because ships are also predicted to increase in size. Today, only 1 in 5 container ships can carry 7600 or more 20-foot containers. This is expected to increase to about half of all ships (48%) by 2030. These larger ships output more noise than smaller ones and thus further drive up ambient noise levels in the ocean.

Furthermore, the average distance travelled per ton of shipping material is expected to increase, driving up the time that large, high-noise ships spend at sea. This is related to increased globalization and availability of new shipping routes. For example, a planned expansion of the Panama Canal would allow larger ships to travel further distances and into new areas.

The shipping routes of the world. Increased traffic along these routes leads to increased underwater noise. Image from Wikimedia Commons.

While this study focused mainly on large, commercial ships that traverse the open ocean, noise increases in small, coastal, recreational craft are also significant. Though they add less ambient noise to the oceans, their continuous, high frequency sounds can have significant impacts on the nearby shallow-water environments. Further studies of these impacts are greatly needed.

The supertanker Batillus, one of the largest ships ever built. Large commercial ships produce more noise than those of moderate size and are expected to become more common in the coming decades. Image from Wikimedia Commons.

The final estimate for noise increase by 2030 was 87 to 102%: quite a significant amount, and large enough to call for increased management. Proposed strategies include speed reductions in high traffic areas along with the development of inherently quieter types of ships. Though guidelines exist regarding ship noise levels, they are currently not mandatory, so a firmer policy could drive the adoption of these noise-efficient ships. Future research could create standard methods of measuring noise levels that could be implemented at shipping ports. This would improve management effectiveness, and similar practices are already used at airports to measure airplane noise. Overall, this study shows that additional research and policies are required for this important yet little-understood area of marine conservation.

Reference

Kaplan, Maxwell B., and Susan Solomon. “A coming boom in commercial shipping? The potential for rapid growth of noise from commercial ships by 2030.” Marine Policy 73 (2016): 119-121.

Ballast Water Management and Its Implications Regarding Invasive Species Introduction

December 19, 2016/0 Comments/in Conservation, Ocean News /by a.anstett

By Casey Dresbach, SRC intern

Ballast water, either fresh or salt water, and sometimes containing sediments, are held in tanks and cargo holds of ships to increase stability and maneuverability during transit. It’s advantageous in its means to stabilize, increase propeller immersion to improve steering, and to control trim and draft. Often times, cons outweigh the pros in the ballast water process. In regards to the marine ecosystem, ballast water discharge contains many plants, animals, viruses, and microorganisms some of which can be invasive or exotic species that can lead to detrimental ecological and economical effects, as shown in Figure 1.

Figure 1. Depiction of how Ballast Water Management can instigate water pollution of the seas from untreated ballast water discharges

Invasive species are a major threat to biodiversity in the marine ecosystem. Once integrated, they become predators, parasites, and diseases of native organisms. Unfortunately, many of these nonindigenous species (NIS) are spreading across the seaboard. These invasive species are making their way into ballast water of ships globally. These ships are picking up water in one location, carrying their said cargo across the seas (ranging from far to close distances), and then discharging that water at their acquired destination. By doing so, the ships transport a subset of native species from one ecosystem into another, to which they may not be native.

In the 15th century, the shipping industry expanded exponentially and led to an increase in the number of vessels. By the 18th century, the expansion was furthered in steam technology, with the addition of more complex vessels that required more stability efforts. Ballast water was issued to these vessels, consequently increasing opportunities for nonindigenous species to spread.

At the global scale, initial efforts have been underway in the past twenty five years to control unwanted nonindigenous species with the Nonindigenous Aquatic Nuisance Prevention and Control Act of 1990, and later the National Invasive Species Act of 1996. Such policy instigation focused on aspects from mid-ocean ballast exchange to quantitative standards of permitted organism density upon ballast water discharge. Among all, there have been exemptions or exceptions to the proposed policies, including crude oil tankers engaged in coastwise trade.

A study in Alaska was initiated in regards to questionable effects of exemptions. The study focused on determining the “effectiveness of existing shore-side ballast water facilities used by crude oil tankers in the coastwise trade off Alaska.” The results indicated a high risk of NIS transport from ballast water discharged in Prince William Sound, Alaska. Much of the ballast water was discharged along intra-coastal shipping routes that originate on the Pacific Coast of North America from invaded source ports. Prince William’s largest port, Valdez, may serve as a designated area for the secondary transfer of nonindigenous species.

The initial BWM policy was not enforced it was voluntary; the nonbinding guidelines were insufficient and continued invasion and warranted stronger action. With that in mind, the initial efforts of BWM were more of a reactionary process because the invasions had since occurred. On November 21, 2001, the United States Coast Guard (USCG) published its final ruling. Since participation in the voluntary program was insufficient to the success of the program; BWM was now going to become mandatory. With this mandate, vessels (other than those exempted: crude oil tankers engaged in coastwise trade, Department of Defense of USCG vessels, and vessels operating within one USCG Captain of the Port Zone) would be fined or issued a monetary civil penalty up to $35,000.

With growing concern, the IMO (International Marine Organization) developed “The International Convention for the Control and Management of Ships Ballast Water and Sediments,” in 2004, to further protect the marine ecosystem from the transport of detrimental nonindigenous species in ballast water carried by vessels.

In 2005 policy initiatives were furthered, and BWM was mandatory for all vessels in the United States, with the same exemptions as before. By 2008, management and recordkeeping requirements went into place with the hopes of decreasing these risks. However, many of those exempted from the BWM such as the crude oil tanker traffic had their transports undocumented and under-reported. As seen in Figures 2 and 3, exemptions from management have negated these efforts to reduce invasion risk. Studies found a 440% increase in ballast water discharge to Alaska in the following year. In a review of ballast water discharge to Alaska (Danielle E. Verna, Bradley P. Harris), a suggestion was made that a precautionary approach to exemptions was of dire need, as well as consistent assessments of the vessels expeditions to reduce the risks of increased invasion.

Figure 2A. Valdez, Alaska water ballast water sources from 2005-2008.

Figure 2B. Valdez, Alaska water ballast water sources from 2009-2012 shows an exponential increase in source volume, primarily due to consequence of exempting a sector.

The inclusion of intra-coastal vessel traffic as well as a better understanding of the NIS risks at stake may reduce the risk of further invasions. The most beneficial impact to the Alaskan industry practices was when BWM became mandatory to all vessels. However, the exemption factor is what threatened to negate the initiative. With continued assessment of vessel behavior and transport as well as documentation and data recordings can help trace back to where this exemption may take their turn in increasing the risk of NIS introduction. Moving forward, policy makers will continue to do their job, but further education among communities will only benefit their obligatory feats.

Resources
International Marine Organization. (n.d.). Ballast Water Management. Retrieved October 24, 2016, from IMO : http://www.imo.org/en/OurWork/Environment/BallastWaterManagement/Pages/Default.aspx
MaxxL, & Hartmann, T. (2014, June 24). Ballast Water. Retrieved October 24, 2016, from Wikimedia Commons: https://commons.wikimedia.org/wiki/File:Ballast_water_en.svg
Reece, J. B., Urry, L. A., Cain, M. L., Wasserman, S. A., & Minorsky, P. V. (2014). Campbell Biology . Boston: Pearson.
Verna, D. E., & Harris, B. P. (11, April 2016). Review of Ballast Water Management Policy and Associated Implications for Alaska. Elsevier Journal .

Fish Avoid Coral Habitats Due to the Presence of Algae

December 13, 2016/0 Comments/in Conservation, Ocean News /by a.anstett

By Leila AtallahBenson, SRC masters student

A thriving coral reef community

The issue

Coral reefs are one of the most diverse, beautiful ecosystems in the world. They contain an array of marine life, swimming around magnificently colored coral. Unfortunately, due to climate change, these once thriving ecosystems are changing. Visible shifts in coral communities usually start with the increasing presence of algae (Figure 2). Although algae are natural and important in healthy coral communities, too much of certain algae can outcompete coral-dwelling symbionts. With decreased coral cover and increased nutrients due to human factors, algae are quickly filling in extra space decreasing coral chances of regaining cover. Corals provide habitat, food, and recruitment cues for many coral reef organisms, and an algae shift will not only hurt the corals, but coral reef communities as a whole.

Threshold of a coral reef community to an algae dominated one.

Experiment and results

Earlier this year researchers wanted to know if associations between coral reef fishes and corals were the same with and without algae present. Butterflyfish, which are known to have a high dependence on corals for food, were exposed to corals with and without two species of algae on them (figure 3). 96% of associations between the fish and coral occurred on corals with no algae. When exposed to both visual and chemical cues, most butterflyfish species preferred to stay where seaweed was not. When the algae were physically removed, new fishes were exposed to the lingering algae chemical cues. One algae attracted butterflyfish, Sargassum polycystum, while the other, Galaxaura filamentosa, a highly toxic algae to corals, still caused fish to avoid the reef. The control reef with no algae or chemical cues still attracted fish.

Butterflyfish in Lord Howe, Australia.

These experiments tell us that butterflyfish use both visual and chemical cues during habitat interactions. Visual algae cues make it more difficult for fish to see coral polyps, and/or to pick up on their chemical cues. Chemical signatures of corals may be altered via stress, seaweed chemicals, or types of defense, given certain algae presence. Coral nutritional value may be decreased when exposed to algae, and these cues may warn butterflyfish from wasting energy.

Outcomes

This is bad news for both corals and butterflyfish. If the majority of butterflyfish feeding occurs on corals without seaweed presence, these healthier corals will have to spend lots of energy in repairing and maintaining their polyps. With increased algal cover, feeding will only intensify on these healthy coral colonies. The increased pressure may lead to decreased efficiency or even mortality. When these corals collapse, butterflyfish will be forced to utilize corals with algae present, thus decreasing their efficiency. This is but one of many examples showing how climate change can drastically effect habitats, forwardly altering entire communities. It’s imperative for people to work together to decrease our carbon footprint and slow the changes of climate change in order to protect these wildly diverse ecosystem.

References

Brooker, R.M., Brandl, S.J., Dixson, D.L. 2016. Cryptic effects of habitat declines: coral-associated fishes avoid coral-seaweed interactions due to visual and chemical cues. Scientific Reports 6.

Science, society, and flagship species: social and political history as keys to conservation outcomes in the Gulf of California

December 10, 2016/0 Comments/in Conservation, Ocean News /by a.anstett

By Cameron Perry, SRC intern

Effective conservation measures must incorporate all stakeholders in the decision making process as well as take into account the social and political atmosphere in which they are created. Conservation measures, even with the best intentions, will fail when they do not take into account these important factors. Montemayer and Vincent (2016) examined a case study from the Gulf of California where a determined conservation lobby and political opportunity led to a rapid establishment of a marine reserve to protect the totoaba (Totoaba macdonaldi) and the vaquita (Phocoena sinus). However, lack of community involvement has led to undermined effectiveness, alienation of indigenous people and risk for the species future.

Biologist holding a Totoaba with a Vaquita at his feet.

The totoaba and the vaquita are both critically endangered species that are endemic to the Gulf of California. The totoaba has suffered from the damming of the Colorado River that greatly reduced freshwater flow since the 1960s. Totoaba are also illegally caught for their highly prized swim bladder which is considered a Chinese delicacy. The vaquita is the world’s most endangered marine mammal and there are only about 60 left in the wild (CIRVA, 2015). This represents a 92% decrease in abundance since 1997. Larger numbers of fishers, versatile gear and boats and open-access conditions have led to overfishing and habitat degradation that has threatened the existence of these species. Currently, there is a reserve established that aims to protect vital habitat for both the vaquita and the totoaba.

Montemayer and Vincent (2016) aimed to study the process that led to the creation of this reserve as well as the socio-political environment in which these actions took place. This research is crucial in order to (1) examine both positive and negative outcomes, and (2) improve future policies.

They found that a series of rapid events with little public involvement in the planning process led to the creation of the reserve in 1993. The reserve was proposed in March 1993 and enacted three months later by a presidential decree. During the second half of the 1990s, an NGO wanted to expand the area of the reserve to protect more habitat for the vaquita and totoaba. Conservation efforts were met with backlash, and this led to a period of socio-political resistance against environmental groups, who were thought to have created a reserve with few benefits and no consultation with local communities. Fishing restrictions were never fully respected by fishers and there are often illegal activities that still occur within the reserve. The lack of incorporating tradition, culture and economic needs of coastal communities has led to unsustainable practices and caused the reserve to not meet its goals.

The Vaquita, endemic to the Gulf of California, has suffered a 92% population decline since 1997. This species is at serious risk of extinction, with only about 60 individuals left in the wild.

This careful analysis of the actions and political environment in which the reserve was created are important to enhance understanding for successful conservation planning in the future. It stressed that the social and political history and full stakeholder involvement must be recognized before regulations can be enacted. Key characteristics of success were defined which included stakeholder involvement, well-defined goals and objectives, a wide and transparent inclusion of scientific knowledge, ongoing monitoring of outcomes and thoughtful design.

Ecological needs should emerge from scientific processes, but it is crucial to identify stakeholders and include their interests before policy suggestions are presented (Montemayer and Vincent, 2016).

References

CIRVA (Comite Internacional Para la Recuperacion de la Vaquita/International Committee for the Recovery of the Vaquita). Scientific Reports of: First Meeting, 25–26 January 1997; Second Meeting, 7–11 February 1999; Third Meeting, 18–24 January 2004; Fourth Meeting, 20-23 February 2012; Fifth Meeting, 7-11 July 2014; Sixth Meeting, 22 May 2015. Available at http://www.iucn-csg.org/index.php/downloads/

Cisneros-Montemayor, Andres and Amanda Vincent. 2016. Science, society, and flagship species: social and political history as keys to conservation outcomes in the Gulf of California. Ecology and Society 21(2)

https://swfsc.noaa.gov/textblock.aspx?Divisions=PRD&ParentMenuId=678&id=21640

To eat or be eaten

December 5, 2016/0 Comments/in Conservation, Ocean News /by a.anstett

By Arina Favilla, SRC intern

When we are hungry, all we have to do is open up the fridge and decide what we want to eat. On the other hand, when fish are hungry, they must leave the safety of their home to forage in areas where there are likely predators awaiting them. They must balance their decision based on hunger and risk factors: is this next meal worth the possibility of becoming prey?

All organisms must eat to meet certain metabolic and energetic demands to survive. The metabolic rate of a fish is influenced by temperature because most fish are ectothermic, meaning their body temperature depends on the surrounding water temperature. As water temperature increases, their metabolic rate increases, which consequently increases how often they forage to meet their energetic requirements. However, foraging also means putting themselves at risk for predation. To investigate how temperature and the impact of predation risk affects foraging activity, Pink & Abrahams (2015) set up controlled experiments with fathead minnows and a likely predator, yellow perch.

Methods

First, they observed foraging and activity rates of minnows exposed to different temperatures in aquarium tanks (39ºF, 59ºF, 75ºF). After food was dispersed by a feeder at the water’s surface, they recorded the number of times the fish would swim to the surface to eat as well as their activity level both before and after feeding for 30 min. They then added the risk of predation to assess how temperature impacts the level of risk fish are willing to take in order to eat. For 15 minutes, they observed the foraging activity of the fathead minnows and recorded whether they used the high-risk feeder closer to the perch’s tank or the low-risk feeder (experimental set-up is shown in Figure 1). These foraging behaviors were compared for minnows at different temperatures (41ºF, 59ºF, 73ºF).

Figure 1. The experimental set up of temperature effect on predator-prey interactions is depicted in the diagram. Fathead minnows were kept in one tank, which was placed close to a separate tank with the yellow perch. Two feeding devices were used: the one closer to the yellow perch tank was considered the high-risk feeder and the one further way, the low-risk feeder. For trials where no predator is present, a divider between the tanks was used to hide the predator.

Results

These experiments showed that temperature significantly influenced the foraging and activity rates of the fathead minnows. The fish exposed to warmer temperatures were more active and foraged more frequently (Figure 2). Although the presence or absence of the predator did not influence foraging rates, it did influence which feeder the fish chose, with more fish choosing the low-risk feeder when the predator was visibly present (Figure 3). However, as the temperature increased for the different treatment groups, more minnows were observed foraging at the high-risk feeder (Figure 3).

Figure 2. This graph shows that in warmer water the fathead minnows fed more often and were more active.

Figure 3. The graphs compare the response of the fathead minnows exposed to different temperatures to the presence and absence of the yellow perch. The top graph (a) shows that temperature did not affect whether the fathead minnows fed at the high-risk feeder or at the low risk feeder. The bottom graph (b) shows that with the predator visibly present, the fathead minnows preferred to feed at the low-risk feeder at cooler water, but in warmer water, they discriminated less between the feeders.

Outcomes

This study shows that temperature influences how much risk of predation is weighed in a fish’s decision to forage. At higher temperatures, fish are hungrier due to higher metabolic rates and are more likely to risk predation in order to feed because they don’t want to die of starvation. Predators have the potential to affect the structure of ecosystems both through their foraging as well as their effects on the behavior of their prey. Better understanding these prey-predator interactions and how environmental factors, such as temperature, influence them is critical in understanding ecosystem dynamics and predicting ecosystem responses to future environmental changes.

Reference

Pink, Melissa, and Mark V. Abrahams. “Temperature and Its Impact on Predation Risk within Aquatic Ecosystems.” Canadian Journal of Fisheries and Aquatic Sciences 73.6 (2016): 869-76.

Re-evaluating the health of coral reef communities: baselines and evidence for human impacts across the central Pacific

December 2, 2016/0 Comments/in Conservation, Ocean News /by a.anstett

By Shannon Moorhead, SRC Masters Student

In the past several decades, it has become clear to researchers that populations of reef-building corals have suffered significant declines worldwide. In the 1970s, coral covered on average,50% of benthic habitat (the sea floor) in the Caribbean; in the early 2000s, this was reduced to an average of 10%, with an estimated 80% decline in total cover throughout the Caribbean. Similar observations have been made in the Pacific, with an estimated decrease from 43% coral cover on average in the 1980s, to 22% cover on average in 2003. These declines are caused by a large variety of both global and local threats. Globally, increasing temperatures, ocean acidification, sea level rise, and disease outbreaks have caused mass coral mortality events and decreased rates of calcification – the rate at which coral grows its calcium carbonate skeleton. In addition to these worldwide stressors, corals face local threats such as overfishing of important grazers and predators, elevated nutrient levels, and increasing amounts of terrestrial sediment in coastal waters. These human impacts kill corals either directly or indirectly, by creating conditions that allow faster-growing algae species to thrive and overtake corals. In some cases, this algal growth can lead to a phase-shift: a change in ecosystem composition and function when macroalgae replaces corals as the dominant benthic cover. Because of this, the majority of studies done to assess reef health have focused only on percent cover of macroalgae and corals. However, recent research indicates that when coral cover declines it is rarely replaced solely by macroalgae and studies have shown that coral and macroalgae together only comprise 19-55% of the reef benthos, organisms that live on the sea floor.

Figure 1. (a) Theses images show hard coral and macroalgae, the two groups most often used to assess reef health. (b) These images show reef builders and fleshy algae, which can be used to assess reef-health with a more community-based approach.

Methods

In this study, Smith et al. also investigated percent cover of other members of the benthos: crustose coralline algae (CCA) and turf algae. Turf algae have a negative impact on coral cover, by growing over and smothering adult corals and preventing the settlement of larval corals. On the other hand, CCA, which produces calcium carbonate like corals, promotes reef resilience by stabilizing reef structure and creating a place for coral larvae to reside and grow, because there are many coral species whose larvae prefer to settle on some types of CCA. Smith et al. considered the cover of all four groups (coral, CCA, turf algae, and macroalgae) to compare central Pacific reef communities surrounding uninhabited islands with communities that surround populated islands and suffer from significant anthropogenic, or human-caused, stressors. Specifically, they examined whether cover of reef-builders (CCA and coral) and fleshy algae (turf and macroalgae) were inversely related, as well as whether the two groups were more common in the absence or presence of human populations.

Figure 2. (a) A map of the five island chains and 56 islands from which data were collected for this study; (b) 17 Hawaiian Islands, (c) 21 islands from the Line and Phoenix Islands, (d) six islands from American Samoa, and (e) 14 islands in the Mariana Archipelago. Stars represent inhabited islands while circles represent uninhabited islands.

Results

Smith et al. evaluated reef communities of 56 islands from five central Pacific island chains between 2002 and 2009 and acquired some surprising results. While coral cover was higher on uninhabited islands, there was not a significant difference between the two. Macroalgae cover varied by archipelago: while there was greater macroalgae cover on populated islands in the Line and Mariana Islands, the Hawaiian Islands and American Samoa had higher macroalgae cover on uninhabited islands. In addition, there was no significant relation seen between total coral and macroalgae cover, contradicting previous ideas that macroalgae directly replaced coral on degraded reefs. However, the average cover of reef-builders was significantly higher on uninhabited islands versus inhabited islands, while the average cover of fleshy algae was significantly higher on inhabited islands versus uninhabited. This result suggests that local anthropogenic stressors play a direct role in changes to the benthic community, and potentially reef health.

Outcomes

In this study, the authors suggest that a good indicator of reef health is net accretion, where the reef-building organisms are building calcium carbonate skeletons faster than they are being eroded. Because it appears that inhabited islands have a lower abundance of reef-building organisms, the reefs surrounding these islands are not as healthy as those near uninhabited islands and may have a harder time bouncing back from large-scale disturbances such as bleaching events and typhoons. Local management on inhabited islands should consider this when developing management strategies and work towards improving the resilience of their reef ecosystems. This research also demonstrates that percent coral and macroalgae cover are not always reliable indicators of reef health; instead management should take a more holistic approach and evaluate other members of the benthos when assessing reef health, in addition to measuring indicators of reef resilience such as coral growth and recruitment, which will help managers predict trends and changes in the structure of the benthic community of coral reefs.

References

Smith, J. E., Brainard, R., Carter, A., Grillo, S., Edwards, C., Harris, J., . . . Sandin, S. (2016). Re-evaluating the health of coral reef communities: baselines and evidence for human impacts across the central Pacific. Proceedings of the Royal Society of London B.

Marine Protected Areas Play a Crucial Role in Conservation and Fisheries Management

November 28, 2016/0 Comments/in Conservation, Ocean News /by a.anstett

By Abby Tinari, SRC Intern

A cartoon by Jim Toomey illustrating the importance of marine protected areas.

Marine protected areas (MPAs) are put in place to protect natural resources from anthropogenic impacts. They play a crucial role in biodiversity conservation and fisheries management, allowing for the protection of nurseries and breeding grounds for rare or commercially important species.

Introduction
MPAs attempt to maximize fishery yields while protecting against overfishing and fishery collapse. In turn, this aims to provide a sustainable market, as well as combat the negative evolutionary effects of fishing. MPAs have arbitrary borders; they are not permanent structures, fish can pass through the borders and therefore spillover into areas outside of the MPA, protecting fish in other areas as well. They attempt to increase connectivity between communities and biodiversity of the area and its surroundings. In their research, O’Leary et. al. found that an objective of MPAs beyond protection and conservation is to satisfy policy makers, workers, and environmentalists, who are all stakeholders in MPAs. Often in areas where MPAs are to be established, waters have been and still are a major source of income for many families. The creation of a marine protected area does not (and should not) mean the taking away of that livelihood, but rather an attempt to help it last far into the future.

The Research
The globally adopted Convention on Biological Diversity (a United Nations, UN, program) has a target to make 10% of the marine environment into a marine protected area by the year 2020 (O’Leary et al., 2016). In O’Leary’s study, his team performed a literature search to determine if this 10% goal was sufficient to protect and preserve biodiversity, ecosystems and achieve different socioeconomic priorities. If the 10% UN goal was not adequate the authors looked to see what the percentage of MPAs that needed to be protected in order to meet the most objectives. Just marine environments were studied. Studies were taken from around the world in both temperate and tropical climates.

The UN’s 10% goal, although a good start does not provide nearly enough protection to support all of MPAs objectives, just as indicated by previous reviews in 2003 and 2010 (O’Leary et al., 2016). To achieve the different sustainability objectives, 30% – 40% of area devoted to MPAs is much more likely needed. (Figure 1). The average and the median were consistently in the 30% to 40% range, indicating, if all objectives were to be met, this would be the ideal MPA percentage range. If the surrounding areas outside of the MPA, as well as inside, are managed properly the lower percentages of MPA are likely to work. The MPAs burden will be lessened with proper management and enforcement both in and outside the area. Within the literature, temperate and tropical regions were studied and those papers were compared. The authors found that no significant difference in the amount of MPA percent coverage was found in terms of their geographical region. MPAs are just as important and effective in accomplishing their objectives in South Florida as they are in the Mediterranean Sea.

Figure 1 – MPA coverage and the subsequent objectives

With greater MPA coverage worldwide, how well the areas meet the objective in the study should increase. MPAs have the ability to contribute greatly to fisheries through protected nurseries and spawning ground that lead to an increase in biomass for fishing. For an MPA to be successful, however, it must have support and input from all stakeholders, so that a compromise can be made with minimal conflict from the parties. The authors note that this finding is simply a perspective, and is in no way a recommendation on what the UN’s target should be.

References

http://oceanservice.noaa.gov/news/weeklynews/may09/mpalist.html

O’Leary, B. C., Winther-Janson, M., Bainbridge, J. M., Aitken, J., Hawkins, J. P., & Roberts, C. M. (2016). Effective Coverage Targets for Ocean Protection. Conservation Letters, n/a-n/a. doi:10.1111/conl.12247

Individual, unit and vocal clan level identity cues in Sperm Whale Codas

November 25, 2016/0 Comments/in Conservation, Ocean News /by a.anstett

By Ryan Keller, SRC intern

The social calls produced by sperm whales consist of three or more broadband overlapped clicks, called Codas. It is believed that certain codas are used to call certain individuals within a unit rather than a broader class of codas which are to all whales in the area. During social learning whales will “babble” and produce many indistinct codas before mastering the skill and eventually producing the specific calls much like a human baby making noises before learning specific words. In order to know what message each specific coda transmits further research needs to be done. By observing social interactions and behavior while simultaneously identifying what codas are being produced it should make their meanings evident.

As seen above, a Sperm Whale (Physeter microcephalus) breaching. The head of the sperm whale contains a waxy like substance called spermaceti which it uses to focus and amplify the clicking noises used for communication and echolocation. Source: Wikimedia commons.

Gero et al. (2016) examined codas of sperm whales in the Caribbean, focusing on male and female social groups. The study took place along a 2000km² area along the coast of Dominica over winters from 2005-2010. Acoustic recordings of echolocation clicks made during dives as well as the codas produced at the surface when the whales. By comparing certain aspects of the echolocation clicks and comparing them to the codas they were able to assign the codas to the specific animals that were making them. They identified over 70 different types of codas with the ones containing 4,5 clicks to be the most common.

It appears that the whales will make these sounds in a duet like fashion and mostly during social interactions or at the surface, not when they are deep hunting for food. Males live most of their lives in solitary while females may travel in groups of two or more called “units”. These units have similar but distinct dialects of codas. This causes segregation between different units as they will only associate with each other if they have the same dialect.

Pictured above: a mother Sperm Whale and her calf swim near the surface. Sperm whales have complex social hierarchies and communicate using various clicking noises called codas. Source: Wikimedia commons.

Social interactions and communication is most complex and through with primates, especially humans. We are just starting to fully understand just how complex many other species social structures are. More research is needed to figure out the specifics of codas and what each one means. We have always just assumed that we are the only species with a language and dialects but it seems that we may not be alone when it comes to this complex and arguably most important social tool.

Reference

Gero S, Whitehead H, Rendell L (2016) Individual , unit and vocal clan level identity cues in sperm whale codas. Royal Society Open Science, 3, 1–12.

https://upload.wikimedia.org/wikipedia/commons/6/61/Physeter_macrocephalus_jumping.jpg

https://upload.wikimedia.org/wikipedia/commons/b/b1/Mother_and_baby_sperm_whale.jpg