What is it about?
Humans have overloaded the world's plant nutrient flows, which caused clear coastal waters to loose underwater plants. These plants were replaced by small floating photosynthesizing microorganisms (algae and bacteria). We studied if we could grow underwater plants in such turbid waters and if the plants would lower the amount of the competing small floating algae. We found that we could get underwater plants to grow, and that they produced more oxygen compared to small floating algae during the day. However, small floating algae would still be present and most of the oxygen was consumed during the night. We argue that in such coastal waters, plant nutrients are still too high either from adjacent farm land or from within the bottom of the water body.
Featured Image
Photo by The Tampa Bay Estuary Program on Unsplash
Why is it important?
Our water bodies are threatened by global warming, overloading plant nutrients and newly introduced species that affect the food web. We need to understand if we can get underwater vegetation growing again, which would be more stable compared to water bodies with a lot of floating small and large algae. Our results indicate that the water bodies are still far from recovering and that they need more protection to reach their original clear water state.
Perspectives
We were very surprised to find that, both underwater plants and floating small algae would produce similar amounts of oxygen during the day, but also consume it during the night. This finding gave us an idea that internal processes in water bodies are still too different from their original state. However, it also open the opportunity to use targeted measures in restoring these water bodies. Future works should also include treatments with different amounts of nutrients or animals that graze on plants and algae.
Maximilian Berthold
Mount Allison University
Read the Original
This page is a summary of: Dynamics of primary productivity in relation to submerged vegetation of a shallow, eutrophic lagoon: A field and mesocosm study, PLoS ONE, May 2021, PLOS, DOI: 10.1371/journal.pone.0247696.
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Resources
Oxygen production assays in bentho-pelagic mesocosms and the Zingster Strom (southern Baltic Sea) in 2014
This data set contains the measured oxygen saturation concentration, and the calculated oxygen concentration corrected for temperature and salinity (according to Benson and Krause, 1984) of one ecosystem site (Zingster Strom, Darss-Zingst lagoon system, southern Baltic Sea) and six bentho-pelagic mesocosms close by. Temperature correction was based on simultaneous measured temperature values, salinity stayed constant in the mesocosms, and salinity correction in the ecosystem was based on daily values. The mesocosms were either phytoplankton, or macrophyte dominated (each n = 3). Measurement intervals were every 5 min (mesocosms) to 10 min (ecosystem). Additionally, Chlorophyll a were included where available and reported as daily values (Zingster Strom n= 365, mesocosms each n = 10), or fitted values (mesocosms, based on available daily values).
Mesopredator‐mediated trophic cascade can break persistent phytoplankton blooms in coastal waters
Follow-up work on how different animals interact in coastal water bodies and how they can be used to lower the amount of floating algae.
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