Adaptability of Marine Organisms to Climate Change

Adaptation Of Marine Organisms Still Insufficient To Ensure Ecological Integrity In The Face Of Climate Change
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Introduction
The incessant release of anthropogenic greenhouse gases has devastated marine and land ecosystems for decades. The marine ecosystem absorbs approximately 93% of the heat energy produced by human and natural activities (Poloczanska et al., 2016); moreover, marine water absorbs most of the anthropogenic emissions of carbon dioxide; as a result, oceanic acidification has produced devastating chemical changes for the marine organisms (University of Plymouth, 2011). Even though scientists have observed the development of adaptive ability in marine organisms to tackle this change in the marine environment, uncertainty about the success of these adaptations persists (Palumbi et al., 2019).
Changes in seawater composition characterized by lowering p H, oxygen concentration, and rising temperature deteriorate marine organisms’ ability to maintain homeostasis. Subsequently, the damaging effect of climate change on marine living organisms is becoming noticeable; development of dead zones, bleaching of coral reefs, and reduction in growth across a wide range of marine species (US EPA, 2022). As the current pace of climate change indicates, the adaptability of marine organisms to cope with the negative impact of climate change is bound to mismatch this pace. The inability of marine organisms to show phenology fluctuation in response to variability would cause devastation in the marine ecosystem, leading to disturbance in the natural food cycle of the land ecosystem (Wang, 2022). This scientific reality highlights that marine organisms may be unable to cope with the rapid changes in the oceanic environment caused by climate change due to their insufficient adaptability. This demands a comprehensive review of the issue in the light of scientific facts.
Adaptability of Marine Organisms to Climate Change: A Critical Literature Review
Compared with the terrestrial environment, the marine environment faces the impact of climate change the most, which has produced unprecedented and rapid changes in the marine ecosystem. An increase in the concentration of dissolved carbon dioxide in marine water has caused acidification of marine water, which change the carbonate chemistry of ocean water; consequently, the ability of marine organisms to produce shell would be highly affected (Poloczanska et al., 2016; Harvey et al., 2014). The decrease in the calcification process of significant marine living organisms such as corals and coccolithophores reduces the productivity of the ocean ecosystem. Moreover, since oceans absorb approximately 30% of anthropogenic carbon dioxide, this absorption lowers the oxygen concentration to a critical level leading to devastating changes in the lifecycle and life expectations of marine organisms (Poloczanska et al., 2016).
The negative impact of climate change changes on marine ecosystems also includes a noticeable reduction in body sizes of marine organisms, changes in reproductive patterns, and earlier spring and delayed autumn events (Poloczanska et al., 2016). Scientific experiments have verified the role of lowering pH level in inducing changes in reproductive patterns; for instance, in a study conducted on the changes in metabolic rates of sea urchins caused by acidification of marine water, scientists found a drastic increase in the metabolic rate of larvae of sea urchin living in low pH marine water. This adaptation was caused by maintaining hydrogen ion homeostasis under acidic water requires higher energy (Palumbi et al., 2019). This observation manifests the negative impact of climate change on marine life and the extent of the adaptive response of marine life.
Acidification of marine war caused by the absorption of anthropogenic carbon dioxide also slows the growth rate of marine organisms; in this regard, one study finds that due to higher concentrations of hydrogen ions, sea urchins face difficulties in the calcification process. As a result, the formation of hard spines slows down, making swimming, feeding, and defense highly difficult for these marine animals (Palumbi et al., 2019). In one similar study, scientists observed the changes in the reproductive and growth pattern of a colonial marine animal called bryozoan (sea mat) Celleporella hyaline. The study used an artificial environment to provide them with water with low pH and higher temperature; the observation revealed that lower pH caused a significant decline in the growth process of these organisms (University of Plymouth, 2011). This experiment verified the development of negative adaptive responses in marine organisms against climate change.
The colonies used in this experiment also showed a remarkable adaptive response to the change in the marine environment by producing a more significant number of male organisms; this adaptive behavior is termed reproductive investment (University of Plymouth, 2011). This observation also verifies that marine organisms have the ability and sensitivity to respond to temperature increases and water acidification. However, this observation also shows that this adaptive response may not be sufficient to enable these organisms to survive. A grave aspect of these detrimental responses of marine organisms is that the negative effect of climate change will continue to increase even if greenhouse gas emissions are reduced to 1.5 Celsius by 2100 as per the Paris Agreement (Roberts et al., 2017). In this way, the current trend of climate change further signifies the reality of its negative impact on marine ecosystems.
The adaptability of marine organisms to changes related to climate change and global warming has become an evident phenomenon; the finding of PISCO-supported research reveals a tremendous genetic diversity of marine animals along the North American west coast. This study also found that marine organisms show adaptation at gene function, expression, and diversity levels (Palumbi et al., 2019). Another study drew a global map to reflect the level of adaptive responses made by marine organisms to climate change. The map indicates equivocal response and no response of marine organisms related to abundance, distribution, calcification, and other parameters. The colors used to reflect consistent, equivocal, and no-change responses are dark blue, light blue, and pale yellow, as shown in the figure below.
Figure 1 Global Distribution of Marine Ecological Impact of Climate Change (Source: Poloczanska et al., 2016)
The adaptability of marine organisms to climate change is observable at several levels, including biochemical responses, gene expression, cellular processes, and organ function. However, changes at genomic and biochemical levels are the most initial and prominent responses. For instance, the ocean's acidification impact on reef-building coral, Acropora millepora appeared first at cellular and genomic levels before any changes in the phenotype (Harvey et al., 2014).