Sea Urchin Growth: Polluted Water's Impact

Sea urchins are sensitive to changes in their environment, and their survival is crucial for maintaining the balance of marine ecosystems. While climate change-induced alterations in salinity levels affect sea urchins' adhesive abilities and movement, pollution from plastic contaminants and toxic elements in sediments also pose significant threats to their growth and development. The presence of pollutants in the water and sediment can lead to developmental abnormalities and even death in sea urchin larvae. With their role in shaping marine communities and the importance of coral reefs, safeguarding sea urchin populations is essential for preserving biodiversity and maintaining healthy ecosystems.

Sea urchins are very sensitive to water quality

For example, heavy precipitation can cause large amounts of freshwater to enter nearshore ecosystems, altering the concentration of salt in the ocean waters and reducing salinity levels. Even slight changes in salinity can impact the ability of sea urchins to attach their tube feet securely to their surroundings. This becomes a matter of life and death for sea urchins, as they rely on their adhesive structures to move in the wave-battered rocky areas near the seashore.

Research conducted by Syracuse University biologists explored the effects of differing salinity levels on sea urchin adhesive abilities. They separated sea urchins into ten groups with varying salinity levels, from normal to very low salt content. The researchers tested the righting response, locomotion, and adhesion of each group. They found that low salinity negatively impacted the righting response, movement, and adhesive ability of sea urchins.

Additionally, sea urchins are sensitive to oxygen levels in the water. Studies have shown that high levels of oxygen do not buffer the negative effects of sediment-bound pollutants on sea urchin larval growth. Accumulation of pollutants in sediments, combined with poor water exchange, poses a significant environmental threat to sea urchins. Sea urchins are also affected by the presence of potentially toxic elements (PTEs) in marine sediments, which can negatively influence the environmental quality of their habitats.

They are used as indicator organisms in public aquariums

Sea urchins are extremely sensitive to water conditions and are used as indicator organisms in public aquariums to determine whether the system is functioning properly. Sea urchins are highly sensitive to air and direct sunlight and are very particular about water quality and cleanliness. They are the first to show signs of stress, which are visible when their spines are laid down or shed.

Sea urchins are not efficient consumers, and their fecal material supports a large bacteria population. Therefore, it is essential to ensure good water circulation and filtration in their tank. The tank can be any height as long as there is proper water circulation and filtration. The water in the tank should pass through a UV sterilization unit at least once every half hour, and one-tenth of the seawater should be replaced with new seawater every week. The water level should be higher than the height of the sea urchin, as no water circulation can be deadly for the sea urchin.

Additionally, it is crucial to maintain the correct temperature for the specific species of sea urchin. Some species, like A. punctulata, are used to warmer temperatures and can be maintained at room temperature without refrigeration. On the other hand, some species require a refrigeration system to maintain the correct temperature. When receiving new sea urchins, it is recommended to let them float in their plastic bags on top of the water for about 20 minutes to allow them to adjust to any temperature differences. It is preferable to let them adjust from warm to cold rather than from cold to warm, as the latter can be fatal and induce spawning prematurely.

Sea urchins are sensitive to changes in salinity levels, and their adhesive abilities are affected by differing levels of water salinity. Low salinity conditions negatively impact their righting response, movement, and adhesive ability. Therefore, it is essential to maintain the correct salinity levels in the tank to ensure the sea urchins' survival and proper functioning as indicator organisms.

Climate change is causing weather extremes that are altering sea urchin habitats

Sea urchins are vital for maintaining the balance of marine ecosystems. They are responsible for grazing around 45% of algae on coral reefs. Without them, coral reefs can become overgrown with macroalgae, limiting the growth of corals.

A team of biologists, led by Austin Garner, studied the impacts of low salinity and how it alters sea urchins' ability to grip and move within their habitat. Garner, a member of Syracuse University's BioInspired Institute, studies how animals attach to surfaces in variable environments from the perspective of both the life and physical sciences. The team's study, recently published in the Journal of Experimental Biology, sought to understand how sea urchin populations will be affected by future extreme climatic events.

The team found that sea urchin righting response, movement, and adhesive ability were all negatively impacted by low salinity conditions. Sea urchins rely on their adhesive structures to move in the wave-battered rocky area near the seashore. Even a slight change in salinity can affect their ability to securely attach their tube feet to their surroundings.

In addition to the impacts of changing salinity levels, sea urchins are also affected by other aspects of climate change. The increase in carbon dioxide (CO2) emissions is causing ocean warming and acidification, which impact sea urchin gametes, development, morphology, physiology, and molecular biology. These stressors can have additive, synergistic, or antagonistic effects on sea urchin populations.

Sea urchins are important for maintaining balance within marine ecosystems

Sea urchins are vital for maintaining balance within marine ecosystems. They are responsible for grazing around 45% of algae on coral reefs. Without sea urchins, coral reefs can become overgrown with macroalgae, limiting the growth of corals. The preservation of coral reefs is crucial for coastal protection and the maintenance of biodiversity.

Sea urchins play a significant role in shaping benthic marine communities in the Mediterranean Sea and the Atlantic Ocean. They also represent an important commercial resource. The reproductive cycle of sea urchins includes three main phases: the growing phase, the maturation phase, and the spent/regenerating phase.

However, sea urchins are sensitive to changes in water salinity, and their survival is impacted by low salinity conditions. Climate change-induced weather extremes, such as heavy rains and flooding, can alter habitats by introducing large amounts of freshwater into nearshore ecosystems. These changes in salinity levels affect the adhesive abilities of sea urchins, impacting their movement and ability to attach to surfaces.

Additionally, sea urchins are affected by pollution. The accumulation of pollutants in sediments, combined with poor water exchange, poses a significant threat to their larval growth. The presence of photosynthetic organisms and oxygen production can help mitigate the negative effects of environmental contamination.

In the kelp forest ecosystem, sea urchins play an important, often overlooked role. While they can mow down swaths of kelp, they also break up tough kelp into manageable pieces that can feed other scavengers, known as detritivores. This highlights the complex and multifaceted role of sea urchins in their ecosystems.

They are susceptible to the negative effects of contaminated sediments

Sea urchins are susceptible to the negative effects of contaminated sediments. The accumulation of pollutants in sediments, combined with poor water exchange, poses a significant environmental threat. This is particularly true in marinas, harbours, estuaries, and bays. The presence of photosynthetic organisms and oxygen production may alleviate the adverse effects of contamination on heterotrophic organisms. However, high levels of oxygen do not always mitigate the impact of sediment-bound pollutants.

The sea urchin species Paracentrotus lividus is often used in ecotoxicological studies due to its susceptibility to contaminated sediments. Research has shown that exposure to polluted sediment negatively affects the larval growth of P. lividus. Experiments have also revealed that contaminated sediments can induce morphological malformations in adult urchins, with embryos from exposed adults displaying reduced growth measures.

The negative effects of contaminated sediments on sea urchins are not limited to a single species. The white sea urchin, Lytechinus pictus, has been studied for its response to contaminated sediments. Exposure to polluted sediments resulted in significantly reduced growth measures in L. pictus, indicating toxic effects.

The impact of contaminated sediments on sea urchins extends beyond their physical growth. Research on P. lividus has shown that exposure to polluted sediments can lead to immune system modulation and overproduction of reactive oxygen species (ROS). Additionally, contaminated sediments can affect the expression of genes related to antioxidant and anti-inflammatory responses in sea urchins.

In summary, sea urchins are susceptible to the adverse effects of contaminated sediments. The accumulation of pollutants in sediments, combined with poor water exchange, poses a significant threat to their growth, development, and overall health. This vulnerability underscores the importance of sediment quality monitoring and management to protect sea urchin populations and maintain the delicate balance of marine ecosystems.

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