Reconstruction of Natural vs. Anthropogenic Causes of Past Harmful Algal Blooms and Associated Plankton in Chesapeake Bay Using Ancient DNA Stratigraphy
Over the last several decades coastal regions throughout the world have experienced what appears to be an escalation in the incidence of Harmful Algal Blooms or HABs. HABs can be species that (a) produce toxins linked to death of aquatic wildlife or human seafood poisonings, and (b) species which are nontoxic but cause harm through the development of high biomass, leading to the depletion of oxygen as blooms decay, or the destruction of habitat for fish or shellfish by shading of submerged vegetation. Since monitoring data of HAB events mainly cover the last couple of decades, it is not clear if any increase is due to human activities (e.g., global change or excess nutrients in the water, or the presumed spreading of HABs via ballast water discharge) as opposed to a response to natural variability in climate. In addition, sediment records of past HABs are sparse and rely exclusively on the identification and enumeration of preserved cellular fossils (e.g., cysts of HAB-causing dinoflagellates). Such microfossil-based HAB records are hampered by the fact that most plankton species are fragile and do not leave solid fossils, misidentification of morphologically indistinguishable cysts, as well as dissolution of calcareous dinoflagellate cysts.
In order to overcome these limitations, I propose to use an advanced ancient DNA (aDNA) approach to reconstruct the identity and abundance of HAB species during the last 200 years in the largest estuary in the US known for frequent HAB outbreaks: the Chesapeake Bay. The aDNA record will also reveal the identity and the relative abundance of plankton communities, including larval stages of, for example, oyster known to be negatively affected by those HABs as well as the identification of species grazing and controlling HABs. Using aDNA, it will for the first time be possible to study such trophic interactions between HABs and associated plankton in the past.
Installation of a High-Frequency Radar System at the Martha's Vineyard Coastal Observatory (MVCO)
The dynamics of the inner continental shelf of the coastal ocean play a critical role in establishing and maintaining exchange between the nearshore and the larger coastal ocean offshore. In the past, research in this area has been done exclusively using across-shelf arrays of moored velocity and hydrographic sensors that assume conditions are along-shelf uniform to estimate depth-dependent exchange. Yet, a major unknown in this work has been understanding the effects of spatial variability on circulation and exchange. To address this unknown, Access to the Sea funds will be used to install a High-Frequency (HF) radar system at the Martha's Vineyard Coastal Observatory (MVCO). This HF radar system, made by CODAR Ocean Sensors, measures surface currents over a broad spatial area with minimal infrastructure and operational costs. Radar installations will take place at two land-based sites along the south coast of Martha's Vineyard, as well as one innovative installation on MVCO's Air-Sea Interaction Tower (ASIT), 3 km offshore.
Together, the system will enable continuous measurements of surface currents over a 15 by 20 km area south of Martha's Vineyard at spatial resolutions approaching 300m and starting just offshore of the surfzone. These observations will resolve the scales of spatial variations present in the inner shelf and add spatial context to previous inner-shelf studies of across-shelf exchange. This installation will greatly enhance the capabilities of MVCO and allow new interdisciplinary collaborations on coastal ocean processes.
Evaluation and Deployment of a New Autonomous Underway System for Measurements of the Marine Carbon Dioxide System
Zhaohui ‘Aleck’ Wang
The marine CO2 (carbonate) system plays an important role in affecting global climate through regulating the direction and magnitude of CO2 uptake or release by the ocean. This system is defined by four primary parameters – partial pressure of CO2 (pCO2) or CO2 fugacity (fCO2), total dissolved inorganic carbon (DIC), pH, and total alkalinity (TAlk). Simultaneous measurements of these parameters with high precision and accuracy are required to study and access important biogeochemical processes and impacts of anthropogenic releasing of CO2 (e.g. ocean acidification) in marine environments. A ship-board automated underway system, the Multi-parameter Inorganic Carbon Analyzer (MICA), has recently been developed to measure fCO2, DIC, pH and atmospheric pCO2 simultaneously with the required precision and accuracy.
A new generation of the MICA system (MICA II) is presently being built for improved studies of the marine CO2 system. This proposed work aims to: (i) calibrate the MICA II and evaluate its performance both in the laboratory and at sea onboard a research vessel, and (ii) to initiate a research program to study the CO2 system and monitor ocean acidification in New England coastal waters using the MICA II system in concert with sampling of other important biogeochemical parameters (e.g. nutrients). The proposed work will not only serve to establish the performance of the MICA II system, but will enable the first field deployment of this novel chemical sensor technology, where preliminary data obtained from an important and understudied coastal area will catalyze broader scale studies of CO2 system dynamics along the New England coast.
Zooplankton Patchiness and Ecosystem Dynamics at the Shelf Break
Our long-term goal is to understand the interaction of physical and biological processes leading to patchiness in zooplankton distributions and the consequences of this patchiness to higher trophic levels, especially cetaceans, at the northwestern Atlantic continental shelf break and its canyons. The Northeast Fisheries Science Center (NEFSC) conducts stock assessment surveys for cetaceans and turtles along the New England shelf break every 4-6 years, with the next survey scheduled for the summer of 2010. The NEFSC survey mostly does not, however, provide information on lower trophic levels and the environmental conditions that underlie the abundance and distribution of these top predators. We will capitalize on this timely opportunity to conduct process studies in coordination with the NEFSC survey, aimed at characterizing the distribution, abundance, and community composition of lower trophic levels, especially zooplankton, and assessing the interaction of zooplankton aggregations with higher trophic levels.
Funds from the WHOI Access to the Sea Endowment will support ship time to conduct small-scale surveys of a shelf break region south of Georges Bank, concurrent to the NEFSC 2010 survey. Our surveys will be conducted both within and away from a canyon feature, as canyons appear to constitute especially important cetacean habitat and zooplankton aggregation is often enhanced within them. The surveys will employ our unique complement of biological sampling instruments, including both broadband and narrowband acoustic systems, and nets and an optical system for direct sampling of the zooplankton present. Characterization of the physical environment will be achieved via a CTD and Acoustic Doppler Current Profiler (ADCP). Together, the data from these instruments will allow the quantification of the abundance, distribution, and aggregation structure of zooplankton and nekton, including fish and squid, in relation to physical conditions. Broadband acoustic scattering techniques have only recently emerged for field applications, and the proposed project will represent among the first applications of this technology to the study of zooplankton ecology.
RATS: An Instrument for Autonomous Measurement of the Carbonate System in Seawater
The marine carbon cycle has been a focus of intensive study over the last decade, both because of its role in absorbing anthropogenic CO2 and, more recently, because of the effect of this CO2 on ocean chemistry and biology. Marine chemists have successfully developed standard procedures for very accurate and precise measurement of the CO2 system in seawater using shipboard and laboratory-based measurements. However, while this work was proceeding, it became apparent that discrete sampling of oceanic chemistry failed to characterize short-term variability that could mask long-term trends and bias estimates of process rates. Continuous sampling by autonomous, moored instruments is necessary to account for the effects of these phenomena on carbon and nutrient cycles.
With Access to the Sea funding, I will complete the development of “RATS”, a unique instrument for autonomous, long-term measurement of oceanic CO2. The instrument is designed to make two measurements, pH (the acidity of the seawater), and TCO2 (the total of the various chemical forms of carbon dioxide in seawater). Together, these measurements allow us to calculate such environmentally important water properties as the pCO2 (the partial pressure of carbon dioxide in the water, an important determinant of CO2 exchange with the atmosphere), dissolved CO2 (changes in this quantity reflect biological activity), and the saturation state of seawater with respect to carbonate minerals (important to many organisms, this quantity changes as a result of ocean acidification). The development of the TCO2 component of RATS has been very successful; the pH component needs additional effort to make it viable for long-term, autonomous measurement. With Access to the Sea funds, I will add a revised pH procedure to RATS and carry out in situ testing to demonstrate that RATS meets the exacting requirements for measurement of the marine CO2 system. The work will give WHOI scientists (Martin and McCorkle) a distinct advantage for participation in both the open-ocean and coastal phases of the Ocean Observatories Initiative, and will enhance an important collaboration with Aleck Wang, a new Assistant Scientist in MC&G whose focus is sensor development. It will provide a means of comparing measurements with the instruments developed independently by M. DeGrandpre (U. of Montana). These comparisons will ensure that CO2 measurements from different instruments that may be deployed as part of OOI are made with known and required accuracy. The ultimate goal of this project is to make possible time series CO2 system characterization at sea, with a continuous presence, for the first time.