Intellectual Merit:

The oceans sustain essential ecological processes and have a major influence on energy flows, weather patterns, global climate, and habitability of the planet for humans.  Long-term observational time series are a powerful and necessary tool for investigating the ocean to understand how it changes in time and the underlying drivers. The broad research goal of the Bermuda Atlantic Time-series Study (BATS) program has been, and continues to be, improving our understanding of the “time-varying” components of the ocean carbon cycle. Zooplankton play a key role in the ocean carbon cycle. First, zooplankton are a central component of ocean food webs via their consumption of phytoplankton and as prey themselves for higher trophic levels such as fish, mediating trophic transfer of carbon through the food web. Second, through their metabolic activities (e.g., respiration, excretion, fecal pellet production), zooplankton recycle and export carbon, playing a key role in the ocean’s biological carbon pump. All of these processes are highly dependent on zooplankton biomass and community structure, which vary on multiple time scales.  Thus, the major goal of the zooplankton component of BATS is to document trends and controls on the diel, seasonal, interannual, and decadal scale variability in mesozooplankton (zooplankton >0.2 mm) community structure in the oligotrophic North Atlantic Ocean in response to climate variability. We also aim to quantify the effects of these trends on changes on carbon and nutrient cycles at BATS.

The BATS research program has completed its 36th year, and the zooplankton time series component of BATS has completed its 30th year. During this now 30-year period, total mesozooplankton biomass in the epipelagic zone (upper 0-200m) increased by 27% overall, equivalent to an average increase of 3.2 mg dry weight per year. A few short-term downturns occurred over the course of the time series, and biomass in 2019 was particularly high with currently no clear environmental causative factor. Annual biomass anomalies were negative the most recent two years, and it is possible we are moving into a negative (downturn) phase of the time series, which would indicate there is not a long-term increase in zooplankton biomass but rather a decadal-scale oscillation between high and low biomass. Diel vertical migrating zooplankton reside in the mesopelagic zone (200-1000m) during the day and migrate into surface waters at night to feed (to avoid predators), returning to depth again just before sunrise. As a result, the biomass of zooplankton in the epipelagic zone at BATS nearly doubles each night. There is a statistically significant increase in diel vertical migrator biomass of 47% over the entire course of the time series, suggesting biomass of deep-sea zooplankton is increasing at a faster rate than that of full-time surface resident zooplankton at BATS. Analysis of BATS zooplankton species composition indicates some of the most pronounced diel vertical migrators include krill, amphipods (small crustaceans), and pteropods (pelagic snails). During this grant period we also analyzed larval fishes collected in BATS zooplankton tows.  Springtime abundance of total larval fish abundance at BATS increased over the time series, likely a result of the increase in their zooplankton prey. A biomass-size analysis of BATS zooplankton data was used to examine efficiency of carbon transfer between zooplankton trophic levels. This transfer efficiency decreased during the most recent decade- the 2010’s, which we posit is due to warming and a recent decrease in phytoplankton primary production.

Broader Impacts:

The BATS program makes strong contributions to the field of ocean science by providing high quality ocean observations and data for empiricists and modelers, and a framework from which researchers can conceive and test hypotheses. Indeed, a number of focused process-oriented research programs have spun off from hypotheses arising from BATS data. The data and results have been disseminated to the community through the BATS and the Biological and Chemical Oceanography Data Management Office (BCO-DMO) websites and through publications.

BATS data and results were used in many education and outreach activities. BATS data are incorporated into courses at the Virginia Institute of Marine Science (VIMS), including Biological Oceanography, which is taught each Fall to the incoming class of VIMS graduate students and to undergraduates at William & Mary. BATS data illustrate key course concepts and each year students access the BATS data in this course as part of a paper assignment to analyze a data set from an on-line ocean data repository.  BATS zooplankton samples are displayed, and the program discussed in public talks at annual VIMS Marine Science Day public outreach events, with attendance of over ~1,000 people. An NSF Research for Undergraduates (REU) student completed her project studying temporal change in squid and octopus larvae from the BATS zooplankton time series. Finally, one each Masters and PhD graduate thesis were directly supported.

Last Modified: 11/27/2024
Modified by: Deborah K Steinberg