By Katie Harazin
The EEB POC project seeks to share the work of POC scientists within Ecology, Evolution, and Biology. This includes Black, Indigenous, Latinx, Asian, Pacific Islander, or any scientist of a race or ethnicity identifying as BIPOC. In this blog post, I’m going to highlight some aquatic science articles featured on the @EEB_POC feed. Keep in mind that EEB encompasses terrestrial work as well! Read about some of the great science being done and network with these scientists. If you can, go even further: hire, cite, and fund these amazing scientists. If you want to share your own work, you can check out their Twitter account @EEB_POC, as well as their brief submission guidelines here.
Coral reef benthic community structure is associated with the spatiotemporal dynamics of submarine groundwater discharge chemistry
Florybeth Flores La Valle, Michael B. Kantar, and Craig E. Nelson
Submarine groundwater discharge (SGD) represents the leakage of freshwater aquifers into coastal ecosystems. This “underground runoff” has the potential to carry nutrients, organic matter, metals, microbes, and pharmaceuticals into marine environments. SGD is not the same everywhere, as its strength and composition reflect changes in the tides and the host landmass, respectively. A few studies have looked at the role of SGD on coastal biology, such as phytoplankton, molluscs, worms, seagrass, and even microbes, but there’s still a huge knowledge gap about SGD in tropical coral reef ecosystems.
In this study, the authors use a statistical tool called “empirical orthogonal function” to measure changes in SGD over space and time, specifically with respect to community structures on the seafloor of Maunalua Bay in Hawaii. They find that SGD dynamics within the bay are complicated, but SGD generally lowers biological diversity. SGD introduces three important factors: low salinity, high nutrients (which allows some organisms to prevail over others), and lower pH. For example, more “acidic” SGD seems to prevent the growth of calcifying macroalgae, while soft-bodied zoanthids thrive closer to SGD sources.
The results reinforce previous implications of SGD on habitats, but mostly highlight the fact that high-level statistical analyses are required to disentangle complex variables impacting the distribution of coastal inhabitants. This methodology has great potential for future use in biological surveys, especially with regards for coral reef management.
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Using a space‐for‐time substitution approach to predict the effects of climate change on nutrient cycling in tropical island stream ecosystems
Therese C. Frauendorf, Richard A. MacKenzie, Ralph W. Tingley III, Dana M. Infante, and Rana W. El‐Sabaawi
One of the largest threats of the climate crisis is the change in rainfall around the world, with the wet tropics predicted to experience more variability. Precipitation directly affects streams, and future precipitation change will alter streamflow and stream ecosystems via shifts in the who’s-who of the community and decreases in fauna abundance.
Why does the who’s-who of the community matter? Community composition itself is important for nutrient cycling, as it dictates where the nutrients go—animals eat, excrete, pee, and poo. That means that in a place like Hawaii where reduced rainfall and more flash flooding are forecasted, bathroom habits are likely to change as well.
For slowly changing ecosystems, it’s sometimes hard to take measurements through time, and can also be difficult to predict the future state of a changing environment. Scientists can circumvent this by comparing different environmental regimes using what is called a “space-for-time” approach. In this study, measure the uptake and output of shrimp, caddisfly, and midges to evaluate the demand of nitrogen and phosphorus across a rainfall gradient on the northeast coast of Hawaii Island.
The authors found that lower population density contributes to lower excretion and egestion (pooping) rates in drier streams. In wetter streams, community excretion supplies up to 70% of nitrogen, 10x more than in the drier streams. This is important because tropical streams are already nitrogen-limited, and reduced rainfall due to climate change will likely exacerbate that. Notably, this is the first use of a “space-for-time” approach to assess future rainfall change in a freshwater ecosystem. If the limitations to this approach are addressed, this may be a powerful tool to study ecosystems at risk.
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Sedimentary oxygen demand and orthophosphate release: sustaining eutrophication in a tributary of the Chesapeake Bay
Tiara Moore and Benjamin Cuker
Eutrophication describes a process where an excess input of nutrients (like phosphorus and nitrogen) nourish algal blooms in a body of water. When algae die, they sink, and organisms living in mud that use that organic matter as well as oxygen to produce energy. With stagnant and stratified waters, this results in reduced bottom-water oxygen (hypoxia or anoxia), which decreases biodiversity and harms fish. Anthropogenic eutrophication caused by agricultural runoff, sewage, or wastewater is a huge problem—if you’ve noticed detergents advertised as “phosphate free,” this is why.
Exacerbating the problem is the fact that reversing eutrophication is exceptionally difficult, even if the initial nutrient input decreases. The decomposition of organic matter releases phosphate back into the water column and re-fuels algae, continuing the cycle of “eutrophication syndrome.” This brings up a lot of questions: how much oxygen is used, and what is the extent of phosphorus release from sediments? How do multiple stressors work synergistically to create or maintain eutrophication and hypoxia?
Hypoxia has been observed in coastal systems, including Chesapeake Bay and its tributaries. During the summer, this hypoxia intensifies as waters stratify and reduce oxygen supply to bottom waters. In this study, sediments from the Chesapeake Bay were incubated at seasonal temperatures so that oxygen demand and phosphorus release could be carefully monitored.
The results show high oxygen consumption paired with substantial phosphate release. This implies nutrients from sediments may be enough to sustain eutrophication without any external input. Understanding the sediment feedback loop is critical for environmental planning, particularly since curtailing nutrient pollution alone may not mitigate environmental degradation in the short-term. Moreover, earlier summers may begin to lengthen the periods of hypoxia and eutrophication. These are both considerations for environmental management of the long-term health of Chesapeake Bay and other coastal areas.
More Aquatic Science with BIPOC Co-Authors Featured on Twitter