Aquatic publication review (26)

Modern ecological research is revealing more and more correlations between climate change and the health of both freshwater and marine ecosystems, with important implications for the future of the environment. The North Temperate Lakes Long-Term Research Program (NTL-LTER) is providing important insights into aquatic invasive species. Some of them may initially occur in small populations, but under the influence of environmental changes, they spread rapidly, disrupting the balance of ecosystems. In turn, research on the brain microbiome of salmonids reveals new relationships between microbes and the host’s nervous system, which can affect its health.

Human activities are also reflected in aquatic ecosystems, as exemplified by geographic differences in mercury concentrations in fish bodies. In China, fish of lower trophic levels, such as carp, accumulate less mercury than popular predators in the United States. Plastic waste, especially in the form of abandoned fishing gear, continues to pose a threat to marine ecosystems. Persistent organic pollutants (POPs), despite regulations, continue to accumulate in the oceans, especially in the Arctic, leading to long-term ecological impacts, including climate change. Climate variability affects phytoplankton, a fundamental component of marine food webs. Research in the Sargasso Sea indicates that changes in temperature and nutrient availability affect its vertical structure, which is crucial to marine ecological cycles.

1. nine lessons on aquatic invasive species from the North Temperate Lakes long-term ecological research program (NTL-LTER)

M Jake Vander Zanden, Adrianna Gorsky, Gretchen J A Hansen, Pieter T J Johnson, Alexander W Latzka, Alison Mikulyuk, Robin R Rohwer, Michael J Spear, Jake R Walsh, Nine Lessons about Aquatic Invasive Species from the North Temperate Lakes Long-Term Ecological Research (NTL-LTER) Program, BioScience, Volume 74, Issue 8, August 2024, Pages 509-523.

Freshwater ecosystems can be used as model test systems for analyzing biological invasions. Using data from the North Temperate Lakes Long-Term Ecological Research (NTL-LTER) program, the paper’s authors identified nine key lessons for aquatic invasive species. The data collected show that:

• Invasive species are more widespread than existing documentation suggests.
• Invasive species usually occur in low numbers, but can multiply rapidly under environmental changes.
• Invasive species can cause serious and long-term ecological impacts.
• Invasive species affect microbial communities in aquatic ecosystems.
• Water reservoirs are peculiar hot spots for the development of invasive species.
• Vulnerability of an ecosystem to invasion can be assessed based on certain factors.
• Removing invasive species can bring long-term benefits.
• Control of invasive species may be more important than the effects of their presence.

Effective management of aquatic invasive species, including their removal, can yield long-term benefits, although such measures are usually costly and difficult to implement. Nevertheless, well-planned interventions can sustainably improve ecosystem health. The results of the study confirmed that the key to minimizing the negative impact of invasive species is rapid identification and control.

2. a brain microbiome in salmonids at homeostasis

Amir Mani et al, A brain microbiome in salmonids at homeostasis.Sci. Adv.10, eado0277(2024).

Variable bony fish, such as salmonids, enter into unique relationships with microorganisms. Until now, bacteria have been detected in the blood and internal organs of healthy fish, but now, for the first time, they have also been indicated in the fish’s brain. Their amount is comparable to that detected in the spleen, although a thousand times less than in the intestines. Interestingly, the brain microbiome shares more than 50 percent. diversity with gut and blood bacteria. Studies have shown that brain bacteria may have the ability to adapt to specific niches, enabling them to, among other things. supporting fish health by biosynthesizing polyamines.

In the case of king salmon (Chinook), the brain microbiome was found to change according to developmental stage – from juvenile to reproductive maturity. These findings provide new avenues for research into the symbiosis of microorganisms and the nervous system of fish, suggesting that bacteria may play an important role in their ability to respond to environmental microbes.

This study provides a new perspective on the interdependence of the microbiome and nervous system function in variegated animals, which could have significant implications for further research into the ecology and health of these organisms.

3. human activities shape important geographic differences in fish mercury concentration levels

Xiang, Y., Liu, G., Yin, Y. et al. Human activities shape important geographic differences in fish mercury concentration levels. Nat Food (2024).

The study, the results of which were published in Nature Food, analyzed the impact of human activities on the geographic variation of mercury (Hg) and methylmercury (MeHg) concentrations in fish, with a focus on China and the United States. The conclusions turned out to be surprising. Despite higher emissions, mercury levels in the bodies of fish from China are lower than for individuals from the United States.

A key factor is the difference in food chain structures: China is dominated by fish of lower trophic levels (e.g., carp), which accumulate less mercury, while in the US predatory fish (e.g., tuna) are more common, with higher concentrations of the element. The authors emphasize the importance of local environmental conditions and sources of mercury emissions in different regions. The results may have important implications for public health policy, particularly in the context of food safety and mercury poisoning risk.

4. four decades of Hawaiian monk seal entanglement data reveal the benefits of plastic debris removal

Jason D. Baker et al, Four decades of Hawaiian monk seal entanglement data reveal the benefits of plastic debris removal. Science385,1491-1495(2024).

The plastics that have been produced over the past 65 years contribute to serious health and environmental problems. One significant source of such waste is lost or abandoned fishing gear. Even then, it remains active, leading to frequent cases of marine animals, including the endangered Hawaiian dandelion (a predatory mammal in the seal family), becoming entangled in it. A study by Baker and co-authors compared data on Hawaiian dandelion entanglements before and after intensive cleanup efforts began in the Northwestern Hawaiian Islands.

The study found that entanglement rates decreased significantly in areas where measures were taken to remove abandoned gear. Continuous and intensive fishing waste removal has long-term benefits for marine ecosystems, and shows significant transformative potential in terms of conservation. Clearing these areas of plastic waste is proving to be an effective remedy for marine environments, confirming the validity of the costs incurred and the effort made.

5. exploring global oceanic persistence and ecological effects of legacy persistent organic pollutants across five decades

Xue Zhang et al. Exploring global oceanic persistence and ecological effects of legacy persistent organic pollutants across five decades.Sci. Adv.10, eado5534(2024).

Persistent organic pollutants (POPs) have been widely studied because of their harmful effects on human health and ecosystems. The authors of the study analyzed more than 10,000. POP measurements from 1980-2023 to assess the effects of environmental regulations and their impact on the oceans. Although global POP concentrations are declining, the Arctic regions, including its shelf seas, are the site of their accumulation, suggesting the transport of pollutants from temperate latitudes.

Increased accumulation of POPs in the Arctic can have long-term ecological effects, so it is important to understand their biogeochemical cycles, understand degradation times and transport mechanisms. Studies show that the oceans can transform from sinks to sources of atmospheric pollutants, as well as affect marine ecosystems through bioaccumulation and biomagnification in the food chain. The researchers stressed that monitoring POPs in the oceans, especially in the Arctic, is key to better understanding global trends and developing effective marine conservation strategies.

6. climate variability shifts the vertical structure of phytoplankton in the Sargasso Sea

Viljoen J.J., Sun X. & Brewin R.J.W. Climate variability shifts the vertical structure of phytoplankton in the Sargasso Sea. Nat. Clim. Chang. (2024).

The study, the results of which were published in Nature Climate Change, focuses on the impact of climate variability on the vertical structure of phytoplankton in the Sargasso Sea, based on 33 years of observations. Phytoplankton, which form the basis of the marine food web, is composed of microscopic autotrophic organisms, and thus plays a key role in carbon uptake and oxygen production. Phytoplankton studies have traditionally relied on satellite data, which provide information about chlorophyll on the ocean surface. However, this information is mainly limited to the surface layers of the reservoir, so it is difficult to observe this phenomenon at greater depths.

During these 33 years of research, changes in the vertical structure of phytoplankton have been observed. On the surface of the Sargasso Sea, a decrease in the carbon to chlorophyll ratio has been observed as a result of warming waters, meaning that phytoplankton produce less biomass relative to their chlorophyll content. This is a response to changing environmental conditions, such as rising temperatures and lower nutrient availability.

However, in the deeper layers, phytoplankton have increased their biomass, which may be a response to changes in ocean mixing and rising deep-sea temperatures and other nutrient cycles. Increased biomass in the deeper layers may also mean that phytoplankton have access to more nutrients there, compensating for more difficult conditions at the surface.