Conservation Strategies for a Changing Climate

by Weronika Konwent

     Conservation of marine species, especially as a response to climate change, requires a reliable conception of current and future spatial distribution of species to allow for the protection of biodiversity and the establishment of conservation at the most appropriate sites. Gormley et al. use Species Distribution Modeling (SDM) to predict how Priority Marine Habitats (PMH) in the NE Atlantic might shift and change according to climate change induced changes. Continue reading

Are No-Take Marine Reserves Really Effective?

 

by Weronika Konwent

No–take marine reserves (NTMRs) are established to promote marine biodiversity and to reign in exorbitant fishery behavior through the prohibition of all fishing and resource extraction. In the past several decades, the quantity of NTMRs has risen greatly across the world. While this seems like an obviously positive trend, many regard the existence of NTMRs as controversial. While most NTMR results appear positive, the opposition claims that faulty study design and a lack of objective empirical data may cause inaccurate portrayals of NTMR effects. Continue reading

Partial Protection in Mexican MPA Only Marginally Effective in Restoring Reef Ecosystem

by Katie Huang

Loreto Bay National Park (LBNP) is a marine protected area (MPA) in the Gulf of California, Mexico, which bans fishing in some areas and allows limited amounts in others. However, since only a small region of the MPA is completely protected, it is possible that the benefits of a no-take area do not offset the effects of the permitted fishing. From 1998 to 2010, Rife et al. (2013) surveyed the biomasses of fish in sites within the LBNP and in open control areas and compared the data from before and after the MPA was established. They found that the biomasses of protected and open area fish were not significantly different. Although the biomasses of herbivorous and zooplanktivorous fish increased significantly within the MPA’s restricted area, the authors did not observe changes in apex predator and carnivore biomasses which suggests that the reef ecosystem is still unhealthy even after 13 years of protection. Possible explanations include poor enforcement of regulations as well as the small size of the restricted area, and management solutions should address these issues to make the LBNP more effective. Continue reading

Hawaiian Marine Protected Areas Produce Spillover

by Katie Huang

Marine protected areas (MPAs) can be beneficial to fisheries through spillover effects, which occur when protected fish stocks recover and migrate into open areas. As a result, fishers tend to react by increasing fishing pressure near MPA boundaries to capitalize on these biomass gradients. To supplement previous research on spillover, Stamoulis and Friedlander (2013) studied a Hawaiian MPA with a new seascape approach that incorporated habitat variables, multiple scales of study, and information on fishing pressure. They took visual surveys of fish populations both targeted and not targeted for conservation along random transects and determined their biomass, species abundance, and density in protected and open areas. The authors found that all fish wellbeing measures were observed to be significantly higher inside the reserve. Also, as distance increased from the MPA boundaries, biomass decreased for resource fish but remained constant for non-resource fish, indicating the existence of a spillover gradient. Although fishing was more concentrated near MPA borders, current harvest rates are sustainable for the time being. The authors suggest that similar comprehensive studies be made throughout Hawaii but that further research should also include analysis on larval and egg export, a second benefit to fisheries besides spillover. Continue reading

Do Marine Protected Areas Save Seychelles Sea Cucumbers?

by Neha Vaingankar

Marine protected areas are a major cause of dispute especially in coastal and island regions like Seychelles, off the western coast of Africa. In recent times, tropical regions all over the world have experienced a huge boom in fishing of holothurians (sea cucumbers). Almost all of the holothurian fisheries are considered fully exploited, in decline, or entirely collapsed. The reason for the high demand is for the holothurian’s medicinal purposes as well as its supposed aphrodisiac qualities. In many tropical coral reef regions, locals rely on these invertebrates for their livelihoods. However, due to the density-dependent reproduction patterns and late maturing of these organisms, holothurians are very vulnerable to over-exploitation. Many MPAs were established in Seychelles 20 years ago that pre-date the wave of heavy exploitation in current times. Cariglia et al. (2013) aims to understand the effectiveness of these MPAs and measure the economic value of these holothurians. Continue reading

Protecting Deepwater Fish Populations in Hawaii

by Katie Huang

Starting in 1998, specific types of marine protected areas (MPAs) called bottomfish restricted fishing areas (BRFAs) were implemented throughout Hawaii to address conservation concerns over deep-sea species. Although much research has been conducted on how MPAs benefit shallow reef fish populations, less is known about how protection affects deepwater ecosystems. Sackett et al. (2014) studied four BRFAs of differing ages to determine whether relative abundance, mean length, and species richness of seven commonly exploited species varied when compared to unprotected regions. The authors took video surveys along the deep sea floor in both types of areas and counted the number and type of fish in each. They found that mean fish length Continue reading

Mapping Variations in Thermal Stress in Order to Help Manage Coral Reefs

As ocean temperatures continue to increase in the next few decades, resultant mass coral bleaching will significantly threaten reefs worldwide. Differences in thermal stress among reefs may play an important role in determining the design of marine reserves. By locating reserves in areas less prone to thermal stress, the corals inside reserves may benefit from reduced physical and biological stress, thus maximizing their overall resilience. In their study, Mumby et al.(2011) used maps of variations in thermal stress to develop hypothesis about the future response of corals to each stress scenario. Additionally, they incorporated spatially realistic predictions of larval connectivity among reefs and applied reserve design algorithms in order to create potential reserve networks for a warming environment. The results showed that reef larval dispersal is sufficient to connect reefs from desirable thermal stress conditions into a reserve network. Although such a network is viable, the reserve design is limited in its ability to account for phenotypic and genetic adaptations in corals. Mumby et al. seek to demonstrate how the design of marine reserve networks is influenced by the corals’ ability to adapt to climate change. They provide two hypotheses: that adequate larval dispersal allows marine reserve design to be stratified, and that uncertainty about coral adaptation to rising sea temperatures is a crucial component in designing marine reserve networks.
Mumby, P. J., Elliott, I. A., Eakin, C. M., Skirving, W., Paris, C. B., Edwards, H. J., Enríquez, S., Iglesias-Prieto, R., Cherubin, L. M. and Stevens, J. R. 2011, Reserve design for uncertain responses of coral reefs to climate change. Ecology Letters, 14: 132–140. doi: 10.1111/j.1461-0248.2010.01562.x

            Peter Mumby collaborated with marine ecologists from various institutions to provide an adaptive approach to reef management. All field data were collected at a depth of 710 m from 58 Bahamian sites. Several different strategies were used to test aspects of their hypotheses. A 20-year climatology of satellite-derived sea surface temperature (SST) was used to examine spatial patterns of thermal stress across reef ecosystems in the Bahamas. The information collected was then developed into four contrasting thermal stress regimes. Principles derived from previous laboratory studies were used to hypothesize the response of corals to climate change in each thermal regime. Thus, the authors predict that corals in regime A, experiencing high chronic and low acute stress, will have the most resistance to bleaching. In order to account for uncertainty over coral adaptation and acclimation, Mumby et al. considered three scenarios for testing their hypotheses. They assumed that the response of corals to thermal stress present today will continue into the future, that corals will exhibit limited local acclimation inadequate to adapt to climate change, and a “bet-hedging strategy” where larval connectivity between reefs is identified. To test the feasibility of the proposed reserve networks, the research team employed a 3D individual-based model of larval dispersal adapted for the Caribbean ecosystem. Reserve-selection algorithms were then used to design a conservation network that minimizes the cost of the reserve system and meets the conservation objectives.
            The results from this study demonstrate that a small proportion of the 58 sites, about 15 percent, are a good selection for inclusion into a reserve network. However, it is difficult to develop an optimal strategy that accounts for all the conditions present in the three scenarios. Data show that acute stress is highest in the central Bahamas, while chronic stress is highest to the west near the Gulf Stream. Generally, larval dispersal showed a west-east pattern across the Caribbean. By including thermal stratification and larval connectivity into reserve design, the authors determined that overall network performance greatly improved by as much as sixfold.

            The first hypothesis posited by Mumby et al. proved to hold true; the spatial distribution of thermal stress and larval connectivity are similar enough that networks may be stratified according to the response of corals to bleaching. Furthermore, satellite measurements of SST reveal that there is enough larval supply to generate a reserve network. Results from the second hypothesis indicate that the key difference in response scenarios is not corals ability to adapt to global warming, but the differences between the alternate scenarios. Although the authors provided potential selection sites for reef reserves based on coral adaptation to stress, they maintain that further research is needed in this area. The framework Mumby et al. develop may be adapted to future improvements in research regarding larval connection and coral response to climate change.

Coral Reef Fishes Show Decreased Antipredator Responses to Risk When Exposed to Increased CO2 Levels

Atmospheric levels of carbon dioxide are currently at 380ppm, and are expected to increase within the next few decades. Such increases in atmospheric concentrations result in increased levels of dissolved CO2 in the oceans. Elevated levels of dissolved CO2 increase ocean acidification and reduce carbonate-ion saturation. Scientists predict that these changes will have varied effects on marine species. A number of studies have demonstrated the variability in the responses of different aquatic species to increased levels of CO2. However, most studies have only compared species belonging to different orders. The study conducted by Ferrari et al. seeks to provide a comparison of physiological responses to elevated CO2 among closely related species. By doing so, they can test whether species sharing related life histories and ecology have similar tolerance levels to CO2. The ability to group species according to their CO2 tolerance could play a key role in predicting changes to marine communities in the future. Recent studies have demonstrated that CO2 exposure causes olfactory impairment in a number of reef fish. Given that reef fish rely upon their chemosensory ability to detect predators, any olfactory impairment is expected to increase mortality rates. Ferrari et al. tested the effects of CO2 exposure on the antipredator responses of four damselfish species; their research revealed that contrary to expectations, the four congeneric species varied drastically in CO2 tolerance. Additionally, using Pomacentrus chrysurus as a model species, their results suggest that reef fish larvae exposed to high levels of CO2 showed decreased antipredator responses to risk.—Cecilia Ledesma

Ferrari, M. C. O., Dixson, D.L., Munday, P. L., McCormick, M. I., Meekan, M. G., SIH, A. and Chivers, D. P. (2011), Intrageneric variation in antipredator responses of coral reef fishes affected by ocean acidification: implications for climate change projections on marine communities. Global Change Biology, 17: 2980–2986. doi: 10.1111/j.1365-2486.2011.02439.x

Maud C. O. Ferrari and scientists from various institutes collaborated on research submitted to Global Change Biology. The experiments for this study were conducted in November and December 2009 at the Lizard Island Research Station located on the Great Barrier Reef, Australia. Four damselfish species, P. chrysurus, P. moluccensis, P. amboinensis and P. nagasakiensis, were collected in light traps at the end of the planktonic larval stage. Once transferred to rearing aquariums, the fish were exposed to CO2-enriched air for 4 consecutive days. The tested levels of were approximately 700 and 850 ppm, levels of dissolved CO2 predicted under greenhouse gas emission scenarios. Immediately after the treatment period was over the fish were used in the experiment. Ferrari et al. measured the antipredator behavioral responses of the fish by quantifying their foraging, swimming activity, and microhabit use after detection of predator risk cues. These activities represent common antipredator responses in prey fishes. In order to compare behavior and mortality rates of fish exposed to CO2, P. chrysurus were placed on small patch reefs for about 11 hours and their behavior and survival were monitored.

The authors found that all four species showed varied antipredator responses when exposed to levels of CO2 higher than 390 ppm. While P. chrysurus, P. moluccensis, P. amboinensis and P. nagasakiensis all displayed significant losses of antipredator behavior, P. amboinensis remained less affected at CO2 levels of 700 ppm. The activities of CO2-treated P. chrysuru in the field were compared to those of control fish. The comparision indicates that P. chrysuru suffered much higher mortality rates, were more active, moved further and higher away from the reef, displayed higher feeding rates and were bolder than control fish. Thus, the CO2-exposed fish clearly lacked the adaptive antipredator responses to risk cues exhibited by control fish.

P. amboinensis appear as the more sensitive species; at CO2 levels of 700 ppm, it showed a 95% reduction in antipredator response. Meanwhile, at those same levels P. nagasakiensis only showed a 30% reduction in antipredator responses. Given similar history traits between the species, the authors cannot explain the variation in responses. They note that in order to better predict changes in marine communities under increasing CO2 levels future work should focus on the role of physiology in explaining these variations. Additionally, the reduced antipredator behavior observed in the lab translated into decreased survival rates under natural conditions; these fish showed as much as a fivefold to sevenfold incresae in mortality when placed in the reefs. These results indicate that interspecific variation in response to rising CO2 may result in changes to the composition of prey species; this would in turn effect the biodiversity of coral reef communities. However, the impact of increased levels of dissolved CO2 on marine ecosystems will depend on both the magnitude of variation between species and the ability of these species to adapt to changing environmental conditions.

The Potential of Small Caribbean Marine Pro-tected Areas for Ecosystem Preservation

Kopp et al. (2010) examined whether small, established marine reserves could effectively sustain a coral reef ecosystem by enhancing the fish stocks and limiting macroalgae growth. The authors studied two marine protected areas (MPAs) around the island of Guadeloupe, one located around Ilets Pigeon and one in the bay of the Grand Cul-de-Sac Marin, and five non-protected reefs for comparison with the protected reefs. Surveys of the fish and benthic communities revealed that although the mean number of individuals per 100 m2 was about the same in MPAs as in non-MPAs, the mean biomass of herbivorous fishes was significantly larger inside MPAs, indicating the presence of larger fish in the MPAs. The study also reported a significantly lower cover of macroalgae in the MPAs than in the non-protected areas, and a significant negative correlation between benthic macroalgal cover and herbivorous fish biomass. Though there was no evidence in the study of the benefits of MPAs extending over their boundaries, they were shown to increase fish biomass and manage macroalgal cover, which contributed significantly to sustaining coral reef ecosystems. — Rachel King
Kopp, D., Bouchon-Navaro, M., Mouillot, D., Bouchon, C., 2010. Herbivorous fishes and the potential of Caribbean marine reserves to preserve coral reef ecosystems. Aquatic Conservation: Marine and Freshwater Ecosystems 20, 516524.

            Within the two MPAs studied, five reef sites were sampled between 1 and 10 m in depth, and the five non-protected reef sites were also sampled between these depths. Visual surveys of fish were performed twice in both the dry and rainy seasons using a 150 x 2 m transect, which provided estimates of fish abundance in terms of density and biomass. Fish were identified to the species level and their length recorded in 5 cm size classes for fish fewer than 20 cm and in 10 cm classes for fish larger than 20 cm. The biomass of fish was estimated using weight-length relationships from the literature. For scarid fish, the phase (initial or terminal) was also noted. While the fish survey was conducted, the benthic community composition was estimated by recording the types of benthic organisms present at every meter along the 150 m transect.
To analyze the collected data, the authors used a canonical analysis of principal coordinates (CAP), which allows a constrained ordination to be performed on the basis of any distance. The response of the whole fish assemblage in the MPAs was analyzed, followed by examining each species. Benthic cover between MPAs and non-protected areas was compared and a correlation between benthic cover and herbivorous fishes was found using the non-parametric Spearman rank correlation coefficient.
            The mean number of individuals per 100 m2 in the MPAs (87.4±22.3 (SE)) was very close to the value outside the MPAs (86.3±22.3 (SE)). This pattern was also observed for the number of scarid fishes inside and outside the MPAs. However, both the total assemblage of fish and scarid fish showed a larger biomass inside the MPAs. Although a few species had higher abundances outside the MPAs, most had larger numbers and biomass inside the reserves and therefore indicated a significant reserve effect on those species. The size class of species also differed significantly between the two types of areas. Large adults of three species, Scarus vetula, Sparisoma rubripinne, and S. viride, that were also in their terminal phase were only found within MPAs, and Acanthurus bahianus only had medium-sized individuals present within MPAs. The results also showed that the mean percentage of terminal males was 22% inside MPAs, whereas it was only 10% outside the reserves. Significant correlations were also found between coral cover and the biomass of large herbivorous fishes, biomass of large herbivorous fishes and macroalgal cover (negative correlation), and macroalgae and algal turf (negative correlation).

The results indicate that marine protected areas are having a significant effect on the biomass of herbivorous fishes in the Caribbean, which especially indicates their importance as a refuge for larger fish. The importance of even small MPAs is accentuated by the results showing that certain terminal phase fish are only found within MPAs. The coral reef communities were also more stable inside the MPAs due to the larger percent coral cover, increased fish stock, and lower algal cover. This study adds significant support to the need to maintain or increase the amount of MPAs to help preserve coral reef communities.