Departmental Seminar: Big changes for little organisms: how plankton communities respond to extreme states in estuaries

Abstract:

Phytoplankton communities comprise the bulk of primary production in marine environments. However, the community composition of these tiny pelagic producers greatly varies. When the dominant members of the phytoplankton community change, their functional roles can shift. If large phytoplankton cells dominate, these cells directly feed large metazoan zooplankton, like crustaceans. Alternatively, if the bulk of phytoplankton production is led by small cells, the consumers are typically heterotrophic protists. Thus, understanding what drives change to phytoplankton communities is crucial to predicting marine trophic systems.

Plankton are effectively immobile in response to ocean currents and consequently, local changes in the plankton community are tightly coupled to environmental change. There are well established paradigms which predict phytoplankton community change following environmental shifts. However, in estuarine systems, change is driven by freshwater inputs from rivers. These are extremely variable both in frequency and magnitude. In tropical and sub-tropical estuaries, extreme states are becoming more prevalent – like droughts and periodic intense storms. Extreme states extend beyond the typical conditions driving phytoplankton community succession – which makes it critical to develop new insights to how plankton respond.

In this presentation, I will share new results investigating how large rain events and wet periods shift the phytoplankton community. From an experimental study, I show how the different mechanisms of intense storms drive growth and introduction of different phytoplankton groups. Then, with long-term observational data, I share how the phytoplankton biovolume changes across wet and dry periods in a high residence time estuary. Finally, I will discuss how these changes may impact higher trophic levels and the on-going work to study to estuarine trophic interactions.

Biography: 

Dr. Alex Barth is a postdoctoral researcher at the University of Texas at Austin, advised by Dr. Jordan Casey in the Marine Science Institute and Dr. Mevin Hooten in the Statistics and Data Science Department. Dr. Barth received his B.S. at Cal Poly – SLO in Marine Sciences where he studied phytoplankton ecology in coastal upwelling systems. He then completed his Ph.D. in Biological Sciences at the University of South Carolina with Dr. Joshua Stone’s zooplankton ecology lab. His doctoral research largely focused on developing approaches to interpret data from in-situ camera observations which he applied to study mesopelagic zooplankton communities. Now, his research in estuarine systems focuses on developing models to incorporate various data sources to study lower trophic level interactions.