By Hannah Calich, RJD student

The benefits of marine protected areas (MPAs) have been well documented. However, since implementing them usually involves the removal or restriction of certain human activities, their implementation is often controversial. For example, MPA regulations that limit fishing can have negative socioeconomic consequences in fishing communities, which can lead to illegal, unreported, or unregulated fishing (Figure 1). To help avoid these problems managers should consider the possibility of integrating a small number of human activities into MPAs.

Currently most MPA regulations focus on extractive uses, such as fishing, while overlooking non-extractive uses, such as scuba diving or kayaking (Figure 2). Since both extractive and non-extractive uses impact ecosystems as well as local economies, researchers have been investigating what happens when both types of uses are allowed within sections of MPAs. Specifically, researchers in Wales (UK) have used specially designed conservation software to determine the impacts of integrating extractive and non-extractive uses in MPAs (Ruiz-Frau et al., 2015). They also examined how these impacts vary depending on how a MPA is zoned. For example, do MPAs with two zones (e.g., one minimally protected zone and one highly protected zone) impact an ecosystem or economy differently than MPAs with multiple zones that have varying degrees of protection?

Ruiz-Frau et al.’s (2015) results indicate that when MPAs include non-extractive uses (e.g., they allow visitors to kayak or snorkel within sections of a protected area), the negative socioeconomic impacts can be reduced by about 50% compared to when non-extractive uses are not included. Additionally, when MPAs have multiple zones they can continue to support healthy ecosystems while having a lower socioeconomic impact than MPAs with only one or two zones.

Incorporating both extractive and non-extractive uses can significantly reduce the socioeconomic impact of MPAs (Ruiz-Frau et al., 2015). These results have important implications to not only future MPAs but current ones as well. If the socioeconomic impacts of MPAs can be lowered, implementing MPAs will be less controversial and more likely to be accepted by communities, which will hopefully lead to more MPAs being developed.

Reference:

Ruiz-Frau, A., Kaiser, M. J., Edwards-Jones, G., Klein, C. J., Segan, D., & Possingham, H. P. (2015). Balancing extractive and non-extractive uses in marine conservation plans. Marine Policy, 52(2015), 11-18.

by Alice Schreiber, RJD intern

The rapid increase of world population and the large number of already depleted fish stocks pose a significant problem for fisheries currently, and will continue to do so in the future. The growth of responsible and sustainable aquaculture facilities can help to alleviate the strain the human population has on the natural environment while providing reasonably priced seafood to people in developing and developed nations around the world. Unfortunately, there are still some issues facing aquaculture today, the most contentious of which associated with sustainability and waste production. Integrated multi-trophic aquaculture combines traditional fish farming with another species at a different trophic level, usually an extractive species that can get its nutrients from the sunlight or water.

 

In recent years, aquaculture has begun to be a major player in providing food security throughout the world. In 2012, global aquaculture production reached an all-time high of 90.4 million tons; China alone attributed 43.5 million tons of fish for food and 13.5 million tons of aquatic algae that year. Aquaculture growth has been relatively faster in Africa, Asia, Latin America, and the Caribbean; the same regions where population growth has been increasing. Along with the increase in production, the interest in integrated multi-trophic aquaculture is also rising. These systems, abbreviated as IMTA, combine fed aquaculture species with inorganic extractive species, such as seaweeds, cultivated in proximity.  Figure one illustrates a typical IMTA:

Many aquaculture systems tend to require very large amounts of inputs and produce massive amounts of waste. The goal is to essentially close the loop, or make the inputs and outputs as low as possible. “Rather than let huge concentrations of fish manure from, say, salmon cages foul coastal waters, you place shellfish, which filter and are nourished by the manure, slightly downstream from your salmon cages; and then seaweed further downstream still, which takes up remaining nutrients from the manure” (Greenaway, 2009). Another issue with traditional aquaculture is the amount of fish used to make fish feed. However, seaweed can be a source of protein and other ingredients without competing with terrestrial plants and causing price increases. This also could help reduce the need for farmland, irrigation, and fertilizer (Chopin, 2012). Shellfish and seaweed can take the excess nutrients and utilize it, converting it into biomass. Dr. Thierry Chopin states that the solution to nitrification is not dilution, but conversion within an eco-system based management perspective (Chopin, 2008).

 

The waste generated from intensive aquaculture systems needs to be treated and in the past solutions have largely focused on reducing particle load or leaving the dissolved nutrients untreated. Treating effluents is expensive and requires a high degree of technology, so releasing the untreated water is unfortunately a way to cut costs. Macroalgae uses sunlight to build biomass, while assimilating dissolved inorganic nutrients removed from the water. If properly cultured, the seaweed can utilize pollutant nutrients as their food and energy source, clean the water, and be harvested as commercial crops with very little added cost to the producer. Recycling of waste nutrients by algae and filter-feeders is the most economical way to improve aquaculture sustainability.

 

Water quality deterioration as a result of excess nutrients is a key concern in aquaculture systems. Seaweed can be cultivated in the same pond as fish or adjacent to fish cages. The plants absorb particulate organics and dissolved nutrients that would otherwise enter the environment. In a recirculating aquaculture system (RAS),  where water is filtered and reused in the tank, fish are even more at risk from high nutrient levels. Seaweed has the potential to improve culture environment by preventing the deterioration of water quality from waste and particulates. Seaweed assimilates the fish-excreted ammonia, phosphate and CO₂, converting them into valuable biomass. With this treatment, water can recirculate back to the fish ponds or be discharged without endangering the environment (Chopin et al., 2001 and Neori et al., 2004). CO₂ is released by fish through respiration, reacts with water, and forms carbonic acid (H₂CO₂), which leads to a lower pH (Wurts, 1992). When pH lowers, acidity increases, which can easily prove fatal for fish. Excessive phosphorus can cause increased plant an algal growth, resulting in anoxia (low or no oxygen), increased turbidity, effects on fish growth, and toxic cyanobacterial blooms (Guo et al., 2003). Unionized ammonium is particularly harmful as it can pass through the gills into fish, convert back into the ionized for, and cause cellular damage.

The advantages of using seaweeds as the biofilter component of the IMTA systems are now becoming widely accepted (Ridler et al., 2007).  Seaweed can greatly help mitigate eutrophication in polluted areas and reduce harmful fish byproducts. Macroalgae (seaweed) actually sequesters the nutrients out of the water, and then the clean and oxygen-rich effluent of a seaweed biofilter can be recirculated back to the fishponds or discharged safely. In seaweed-based IMTA systems, TAN (total ammonia N, NH₃+NH₄) and the other excess nutrients from the fed finfish/shrimp culture are taken up by seaweed.

Aquaculture is not a perfect industry as of yet. Macroalgae, or seaweed can provide multiple benefits when used in IMTA. Seaweed has potential as food, cosmetics, biofuel, agrichemicals, fishmeal, and is able to function as a biofilter for the aquaculture systems. The IMTA approach to fish farming is proving to be very beneficial economically as well as for the environment. Not only can seaweed help to maintain clean water quality, it can be used to clean up areas with excess nutrients or harmful waste products like ammonium and CO₂. This will likely become the new standard for aquaculture as demand continues to rise and the need for environmentally safe practices increases.

Chopin, T. “Integrated Multi-Trophic Aquaculture (IMTA) – the right move for sustainability?” in Inshore Ireland 4 (3): 20, June 2008.

Chopin, T. “Seaweed aquaculture provides diversified products, key ecosystem functions. Part II. Recent evolution of seaweed industry.” Global Aquaculture Advocate 15 (4): 24-27, July-August 2012.

Greenaway, T. “Closing the aquaculture loop.” Culinate, 5 February 2009.

Guo, Longgen, and Zhongjie Li. “Effects of nitrogen and phosphorus from fish cage-culture on the communities of a shallow lake in middle Yangtze River basin of China.” Aquaculture 226.1 (2003): 201-212.

Neori, Amir, et al. “Integrated aquaculture: rationale, evolution and state of the art emphasizing seaweed biofiltration in modern mariculture.” Aquaculture 231.1 (2004): 361-391.47–131.

Ridler, N., et al. “Integrated Multi− Trophic Aquaculture (IMTA): A Potential Strategic Choice for Farmers.” Aquaculture Economics & Management 11.1 (2007): 99-110.

Wurts, William A., and Robert M. Durborow. Interactions of pH, carbon dioxide, alkalinity and hardness in fish ponds. Stoneville,, Mississippi: Southern Regional Aquaculture Center, 1992.

 

by Laurel Zaima, RJD intern

Harmful algal blooms (HABs) are a large concern for many who live on the coasts. People are told to avoid eating local seafood and contact with the contaminated water. However, the consequences of HABs extend much further than many people realize. HABs are associated with high fish mortality, which disturbs the entire effected marine and coastal ecosystem. During HABs, there are high cell densities of toxin-producing phytoplankton species. These phytoplankton produce a paralytic shellfish toxin (PST) and they are easily ingested by planktivorous fish or filter-feeding organisms. Once the toxin has entered the food web, PSTs can impact multiple trophic levels. (Picture 1: An expansive harmful algal bloom is prominently seen off the coast of Gotland, a Swedish Island in the Baltic Sea.) PSTs are a worldwide concern because they are concentrated and abundant near the coasts and have detrimental affects on aquaculture, fisheries, human health, industries, and economies. In the scientific paper, Impact and effects of paralytic shellfish poisoning toxins derived from harmful algal blooms to marine fish, Costa (2014) assess the fish contamination, fish mortality, and the ecosystem-wide implications of these toxins in order to better understand and help to better manage the damaging effects of PSTs.

Paralytic shellfish toxins are produced in the marine environment by nine dinoflagellate species. Each of the PSTs have slight differences in the structure of their functional groups, which results in different toxicity levels. (Picture 2: The chemical structure of the paralytic shellfish toxins (PSTs)). Fish that are exposed to PST exhibit irregular swim and motor behaviors, such as swimming on their sides or upside down and gaping at the surface. With extensive exposure to PSTs, the toxin causes subsequent paralysis in the muscles. Therefore, PSTs prevent fish from effectively foraging or avoiding predators. Ultimately, the most common result of the toxicity is death.

Fish mortality associated with PSTs have been reported worldwide. Fish species involved in the toxic episodes include planktivorous fish that feed directly on the toxic algae, planktivorous fish that ingested contaminated zooplankton that have fed on the toxic algae, predators species that have fed on the contaminated fish or shellfish, and fish that are artificially fed but were directly exposed to the toxic algae. The PSTs that are produced by harmful algal blooms can modify the predator-prey interactions that can lead to a cascading affect on the coastal food web and community structures in the marine systems. PSTs hold consequences for organisms at various trophic levels from the ability to initiate a top-down or bottom-up trophic cascade. Humans have also been contaminated by PSTs in various countries from ingesting toxic fish. After people were directly affected by PSTs, action towards algal management was implemented in several countries. Countries in South-East Asia have employed laws that enforce the identification and count of the toxic phytoplankton in seawater, a measure of the toxicity in the shellfish, and a constant monitoring of the marine toxins in planktivorous fish before declaring the local fish acceptable for consumption.

The neurotoxic paralytic shellfish toxins have negative impacts on the fish populations and any associated marine and terrestrial organisms. PSTs have an apparent significance on the function of the ecosystem, and therefore, there is an increasing importance in understanding, managing and monitoring the issue. In terms of ecosystem-based management, it is imperative that fish are properly characterized by their levels of PST exposure from direct consumption and through potential intermediate vectors in order to keep seafood consumers safe from the toxins.

Impact and effects of paralytic shellfish poisoning toxins derived from harmful algal blooms to marine fish
P Reis Costa – Fish and Fisheries, 2014