Alexandrium fundyense cysts in the Gulf of Maine: Long-term time series of abundance and distribution, and linkages to past and future blooms

Abstract

Here we document Alexandrium fundyense cyst abundance and distribution patterns over nine years (1997 and 2004-2011) in the coastal waters of the Gulf of Maine (GOM) and identify linkages between those patterns and several metrics of the severity or magnitude of blooms occurring before and after each autumn cyst survey. We also explore the relative utility of two measures of cyst abundance and demonstrate that GOM cyst counts can be normalized to sediment volume, revealing meaningful patterns equivalent to those determined with dry weight normalization. Cyst concentrations were highly variable spatially. Two distinct seedbeds (defined here as accumulation zones with > 300 cysts cm−3) are evident, one in the Bay of Fundy (BOF) and one in mid-coast Maine. Overall, seedbed locations remained relatively constant through time, but their area varied 3-4 fold, and total cyst abundance more than 10 fold among years. A major expansion of the mid-coast Maine seedbed occurred in 2009 following an unusually intense A. fundyense bloom with visible red-water conditions, but that feature disappeared by late 2010. The regional system thus has only two seedbeds with the bathymetry, sediment characteristics, currents, biology, and environmental conditions necessary to persist for decades or longer. Strong positive correlations were confirmed between the abundance of cysts in both the 0-1 and the 0-3 cm layers of sediments in autumn and geographic measures of the extent of the bloom that occurred the next year (i.e., cysts → blooms), such as the length of coastline closed due to shellfish toxicity or the southernmost latitude of shellfish closures. In general, these metrics of bloom geographic extent did not correlate with the number of cysts in sediments following the blooms (blooms → cysts). There are, however, significant positive correlations between 0-3 cm cyst abundances and metrics of the preceding bloom that are indicative of bloom intensity or vegetative cell abundance (e.g., cumulative shellfish toxicity, duration of detectable toxicity in shellfish, and bloom termination date). These data suggest that it may be possible to use cyst abundance to empirically forecast the geographic extent of the forthcoming bloom and, conversely, to use other metrics from bloom and toxicity events to forecast the size of the subsequent cyst population as the inoculum for the next year's bloom. This is an important step towards understanding the excystment/encystment cycle in A. fundyense bloom dynamics while also augmenting our predictive capability for this HAB-forming species in the GOM.

Investigating possible causal relations among physical, chemical and biological variables across regions in the Gulf of Maine

“…However, water masses shift between regions and stochastic events may be more important than regularities in the forcing functions. Contradicting views can be found in Brooks (2009), Ji et al (2013) and Anderson et al (2014 ). Studies by Wong et al (2007) and Valesini et al (2010) as well as studies summarized in Valesini et al address whether regions can be classified based on physical and chemical criteria so that biological characteristics can be predicted from the classification.…”

Some considerations about coastal ocean observing systems

“…Thus, many of these biological sensors are now transitioning to operational status and being deployed in service of monitoring harmful algal blooms, counting individual singlecelled organisms via automated microscopes, or detecting changes in key nutrient or chemical parameters of the coastal ocean (e.g., Anderson et al 2014). In addition to now-standard oxygen and chlorophyll observations, nutrients such as ammonium (NH 4 ), nitrate (NO 3 ), and phosphate (PO 4 ) are being measured in real time via observing system assets (Northeastern Regional Association of Coastal Ocean Observing Systems 2015).…”

“…Ultraviolet spectrophotometry of nitrate (e.g., Johnson and Coletti 2002;Sakamoto, Johnson, and Coletti 2009); in situ wet chemistry (e.g., Hanson [75, 3 2000); flow cytobots that individually recognize, count, and categorize phytoplankton species (e.g., Campbell et al 2013); and molecular sensors for potential toxins (e.g., Anderson et al 2014) are examples of the types of instruments that have been developed and commercialized within the last decade. Of those new classes of sensors, most are focused on coastal areas because of higher power requirements, more onerous operation, maintenance, and calibration, as well as the higher signal-to-noise ratios present.…”

Harmful Algal Blooms in Fjords, Coastal Embayments, and Stratified Systems: Recent Progress and Future Research

“…For instance, in open coastal waters and at a wide spatial scale, cyst distribution patterns of the dinoflagellate Alexandrium fundyense, which is the source of paralytic shellfish poisoning (PSP), have been linked to interannual variability in the intensity and extension of the blooms of this species . Anderson et al (2014) developed a model for empirical forecast of the geographic extent of a forthcoming bloom based on cyst abundances. However, this link varies among species and habitats, and interpretation is complicated by many natural factors, Life-history strategies can also display intraspecific genetic diversity, as recently revealed using molecular tools.…”