Effects of Climate Change on Marine PhytoplanktonRising temperature and CO2 are affecting the physiology of marine phytoplankton species with cascading effects on the rest of marine food chains. Our current work in this area investigates the effects of climate change on phytoplankton metabolites and how those changes alter carbon flows to marine bacteria. This work is in collaboration with Mary Ann Moran and Art Edison at UGA.
Phytoplankton excretion of exometabolites and lysis (releasing endometabolites) are primary sources of labile DOC in the ocean (see Figure). Given a production rate of ~20 Gt C y-1 (40-50% of marine NPP) but a seawater inventory of only 0.2 Gt C (Hansell 2013), the annual organic matter flux via these metabolites is one of the largest steps in the global carbon cycle. In this research, we are asking whether the composition and lability (i.e., rates and efficiencies of bacterial processing) of phytoplankton-derived metabolites are affected by temperature and CO2 levels representing pre-industrial and predicted year 2100 conditions. |
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Ecosystem Mapping
Ecosystem mapping
Productivity of Coral Reefs
Coral reefs are known to be highly productive ecosystems but the exact rates of productivity and the organisms responsible for this productivity have not been studied extensively.
We are working on new approaches to measuring the productivity of coral reefs by scaling up the production rates of individual organisms to reef scale using 3D reconstructions of coral reefs.
We are working on new approaches to measuring the productivity of coral reefs by scaling up the production rates of individual organisms to reef scale using 3D reconstructions of coral reefs.
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Primary Producers on Coral Reefs
Photosynthetic organisms on coral reefs include a range of algae and organisms that form symbiotic association with a group of dinoflagellate algae (Symbiodinium) including corals and gorogonians. We collect these photosynthetic organisms and measure their photosynthetic rates (oxygen production) individually in chambers as shown in the image to the left. |
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Abundances of Photosynthetic Organisms on a Reef
To scale up the measurements of individual primary producers to reef scale, we estimate the abundances of each photosynthetic group (corals, gorgonians, algae, etc) from 3D reef reconscructions. The 3D reef reconstructions are generated from a large number of photographs on the reef using computer vision approaches, and then surfaces are labeled (coral, algae, sand, rubble, etc) with machine learning procedures (Figure 4).
To scale up the measurements of individual primary producers to reef scale, we estimate the abundances of each photosynthetic group (corals, gorgonians, algae, etc) from 3D reef reconscructions. The 3D reef reconstructions are generated from a large number of photographs on the reef using computer vision approaches, and then surfaces are labeled (coral, algae, sand, rubble, etc) with machine learning procedures (Figure 4).
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Sample results of 3D reconstruction and classification of the benthos on Little Grecian Reef in the Florida Keys.
A) Overhead view of a 3D reconstruction of a small section of reef (~10m x 5m) centered on a large Orbicella faveolata colony on the reef crest. B) Results of automated classification of benthic surfaces (Hopkinson et al. 2020). C) Side view of the same section of reef to emphasize the 3D nature of the reconstruction. Example results of taxon-specific gross primary production on a reef in the Florida Keys.
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