Posts Tagged 'review'

A review of mesocosm experiments on heavy metals in marine environment and related issues of emerging concerns

Mesocosms are real-world environmental science tools for bridging the gap between laboratory-scale experiments and actual habitat studies on ecosystem complexities. These experiments are increasingly being applied in understanding the complex impacts of heavy metals, ocean acidification, global warming, and oil spills. The insights of the present review indicate how metals and metal-bound activities impact on various aspects of ecological complexities like prey predator cues, growth, embryonic development, and reproduction. Plankton and benthos are used more often over fish and microbes owing to their smaller size, faster reproduction, amenability, and repeatability during mesocosm experiments. The results of ocean acidification reveal calcification of plankton, corals, alteration of pelagic structures, and plankton blooms. The subtle effect of oil spills is amplified on sediment microorganisms, primary producers, and crustaceans. An overview of the mesocosm designs over the years indicates that gradual changes have evolved in the type, size, design, composition, parameters, methodology employed, and the outputs obtained. Most of the pelagic and benthic mesocosm designs involve consideration of interactions within the water columns, between water and sediments, trophic levels, and nutrient rivalry. Mesocosm structures are built considering physical processes (tidal currents, turbulence, inner cycling of nutrients, thermal stratification, and mixing), biological complexities (population, community, and ecosystem) using appropriate filling containers, and sampling facilities that employ inert materials. The principle of design is easy transportation, mooring, deployment, and free floating structures besides addressing the unique ecosystem-based science problems. The evolution of the mesocosm tools helps in understanding further advancement of techniques and their applications in marine ecosystems.

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Ocean acidification impacts on zooplankton

Rising atmospheric CO2 alters the ocean biochemistry in the process known as ocean acidification (OA). It influences biodiversity at different levels, including zooplankton, which is a key component of aquatic communities and plays a pivotal role in the structure and functioning of marine planktonic food webs as a major link between pelagic primary producers and planktivorous. The effect of OA on the fitness of individual zooplanktonic species has been reported by many studies mostly developed under laboratory conditions. In this context, this chapter reviews the OA effects on zooplankton and describes the potential of natural shallow-water CO2 vents as in situ laboratories. The impact on zooplankton assemblages is shown from a study in the North Atlantic (Azores islands) and the suitability of this area for future studies on marine organisms and ecosystems. Sites with naturally elevated CO2 conditions are described, including which variables and limitations must be considered. Results shown are highly relevant to improve our predictions of the responses of zooplankton to climate change stressors including OA. Future studies including long-term multigenerational exposure to multiple stressors (e.g. increased pCO2 and food shortage) are a priority to understand the adaptation capacity of common species and how the zooplankton communities will shift.

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Economic impacts of ocean acidification: a meta-analysis

This paper presents the first comprehensive review and synthesis of studies that forecast economic impacts of ocean acidification. The changes in seawater chemistry resulting from increased carbon dioxide emissions, collectively known as ocean acidification, will have detrimental impacts to marine ecosystem services. Those services include wild capture fisheries, aquaculture, recreation, shoreline protection, and others. The current literature valuing expected impacts to those services is rather thin and tends to focus on mollusk harvesting and aquaculture. Despite the paucity of studies, we divide all relevant estimates into seven additively separable economic sectors to provide the first aggregate estimate of economic damages from ocean acidification at the end of this century. We perform non-parametric bootstrap to characterize the distribution of estimates within each sector and the aggregation across sectors. We also perform meta-regressions to explore whether estimates provided by these studies are generally consistent with expectations based on ocean chemistry and economic theory. We find a global average of per capita annual losses in the year 2100 between $47 and $58 and we find strong evidence that estimates are consistent with expectations given future emissions and socio-economic scenarios that underlie the original studies.

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Natural and anthropogenic drivers of acidification in large estuaries

Oceanic uptake of anthropogenic carbon dioxide (CO2) from the atmosphere has changed ocean biogeochemistry and threatened the health of organisms through a process known as ocean acidification (OA). Such large-scale changes affect ecosystem functions and can have effects on societal uses, fisheries resources, and economies. In many large estuaries, anthropogenic CO2-induced acidification is enhanced by strong stratification, long water residence times, eutrophication, and a weak acid–base buffer capacity. In this article, we review how a variety of processes influence aquatic acid–base properties in estuarine waters, including river–ocean mixing, upwelling, air–water gas exchange, biological production and subsequent respiration, anaerobic respiration, calcium carbonate (CaCO3) dissolution, and benthic inputs. We emphasize the spatial and temporal dynamics of partial pressure of CO2 (pCO2), pH, and calcium carbonate mineral saturation states. Examples from three large estuaries—Chesapeake Bay, the Salish Sea, and Prince William Sound—are used to illustrate how natural and anthropogenic processes and climate change may manifest differently across estuaries, as well as the biological implications of OA on coastal calcifiers.

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Phytoplankton dynamics in a changing Arctic Ocean

Changes in the Arctic atmosphere, cryosphere and Ocean are drastically altering the dynamics of phytoplankton, the base of marine ecosystems. This Review addresses four major complementary questions of ongoing Arctic Ocean changes and associated impacts on phytoplankton productivity, phenology and assemblage composition. We highlight trends in primary production over the last two decades while considering how multiple environmental drivers shape Arctic biogeography. Further, we consider changes to Arctic phenology by borealization and hidden under-ice blooms, and how the diversity of phytoplankton assemblages might evolve in a novel Arctic ‘biogeochemical landscape’. It is critical to understand these aspects of changing Arctic phytoplankton dynamics as they exert pressure on marine Arctic ecosystems in addition to direct effects from rapid environmental changes.

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Climate change and its impact on the coastal region

Coastal zones are highly populated and among the world’s most diverse and productive environments. Coastal areas include complex ecosystems such as coral reefs, mangrove, salt marshes, seagrasses, etc. Global climate change accelerated by human activities affects the physical, biological, and biogeochemical characteristics of the coastal regions. Consequently the ecological structure, their functions, and the goods and services of the coastal regions are being modified. The ecosystem resilience will be greatly reduced through human impacts as well as rising sea levels, increasing sea temperatures, and other climate ocean-related changes, including prevailing wave activity and storm waves and surges. Sea level rise and increased seawater temperatures are projected to accelerate beach erosion and cause degradation of natural coastal defences such as mangroves and coral reefs resulting in negative effect on the socio-economic aspects of coastal population. Therefore, integrated approaches are essential at various levels to manage the climate change impact on coastal region.

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Resilience of cold water aquaculture: a review of likely scenarios as climate changes in the Gulf of Maine

Climate change is one of the biggest challenges facing development and continuation of sustainable aquaculture in temperate regions. We primarily consider the ecological and physical resilience of aquaculture in the Gulf of Maine (GoM), where a thriving industry includes marine algae, extensive and intensive shellfish aquaculture, and a well‐established Atlantic salmon industry, as well as the infrastructure required to support these economically important ventures. The historical record of sea surface temperature in the GoM, estimated from gridded, interpolated in situ measurements, shows considerable interannual and decade‐scale variability superimposed on an overall warming trend. Climate model projections of sea surface temperature indicate that the surface waters in the GoM could warm 0.5–3.5°C beyond recent values by the year 2100. This suggests that, while variability will continue, anomalous warmth of marine heatwaves that have been observed in the past decade could become the norm in the GoM ca. 2050, but with the most significant impacts to existing aquaculture along the southernmost region of the coast. We consider adaptations leading to aquacultural resilience despite the effects of warming, larger numbers of harmful nonindigenous species (including pathogens and parasites), acidification, sea‐level rise, and more frequent storms and storm surges. Some new species will be needed, but immediate attention to adapt existing species (e.g. preserve/define wild biodiversity, breed for temperature tolerance and incorporate greater husbandry) and aquaculture infrastructure can be successful. We predict that these measures and continued collaboration between industry, stakeholders, government and researchers will lead to sustaining a vibrant working waterfront in the GoM.

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Synthesizing and communicating climate change impacts to inform coastal adaptation planning

Planning for adaptation to climate change requires regionally relevant information on rising air and ocean temperatures, sea levels, increasingly frequent and intense storms, and other climate-related impacts. However, in many regions there are limited focused syntheses of the climate impacts, risks, and potential adaptation strategies for coastal marine areas and sectors. We report on a regional assessment of climate change impacts and recommendations for adaptation strategies in the NE Pacific Coast (British Columbia, Canada), conducted in collaboration with a regional planning and plan implementation partnership (Marine Plan Partnership for the North Pacific Coast), aimed at bridging the gaps between climate science and regional adaptation planning. We incorporated both social and ecological aspects of climate change impacts and adaptations, and the feedback mechanisms which may result in both increased risks and opportunities for the following areas of interest: “Ecosystems”, “Fisheries and Aquaculture”, “Communities”, and“Marine Infrastructure”. As next steps within the region, we propose proactive planning measures including communication of the key impacts and projections and cross-sectoral assessments of climate vulnerability and risk to direct decision-making.

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An extreme decline effect in ocean acidification ecology

Ocean acidification – deceasing oceanic pH resulting from the uptake of excess atmospheric CO2 – is expected to affect marine life in the future. Among the possible consequences, a series of studies on coral reef fishes suggested that the direct effects of acidification on fish behaviour will be the most catastrophic. Recent studies documenting a lack of effect of experimental ocean acidification on fish behaviour, however, call this dire prediction into question. Here, we critically assess the past decade of ocean acidification research regarding direct effects on fish behaviour. Using a meta-analysis, we provide quantitative evidence that the research to date on this topic is strongly characterized by a phenomenon known as the “decline effect”, where large effects have all but disappeared over a decade. The decline effect in this field cannot be explained biologically, but is strongly associated with well-known biases to which the process of science is generally prone. We contend that ocean acidification does not have as much of a direct impact on fish behaviour as previously thought, and we advocate for improved approaches to minimize the potential for a decline effect in future avenues of research.

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Biodiversity distribution patterns of marine phytoplankton and their main threats (climate change, eutrophication and acidification)

Marine phytoplankton is generally defined as the unicellular photoautrophic algae that “wander” drifted by the water body movements. This group accounts for 45% of the annual net carbon fixed by photosynthesis on the Earth, although they represent less than 1% of the photoautotroph biomass. Taxonomically, marine phytoplankton is an umbrella term that includes organisms fairly different from an evolutionary perspective from prokaryote cells, Cyanophyta, as well as eukaryotic organisms belonging to eight major divisions or phyla. They are Haptophyta, Cryptophyta, Bacillariophyta, Chlorophyta, Chrysophyceae, Dictyophycea, Xanthophycea, and Dinophycea. Other common features of the phytoplankton communities, tightly linked to the coexistence of multiple species, is that their abundance distribution follows a power function of the cell mass. One of the main features of the phytoplankton communities is their elevated spatial and temporal variability in comparison to their terrestrial counterparts.

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