Professor Kim Reece’s plenary presentation entitled “Historic and emerging patterns of micro-algal blooms in Chesapeake Bay” gave an overview of the recent observations regarding micro-algal blooms in the lower Chesapeake Bay, with particular reference to two potentially harmful algal species, Cochlodinium polykrikoides and Alexandrium monilatum.
Abstract of the presentation
In recent years several potentially toxic harmful algal bloom (HAB) species have been identified in Chesapeake Bay waters. Notably, blooms of two HAB organisms, Cochlodinium polykrikoides and Alexandrium monilatum, have been increasing in intensity and duration throughout the lower Chesapeake Bay region. These events have coincided with the decline in wild fisheries and expansion of shellfish aquaculture industries in the region. Until the 1990’s, C. polykrikoides blooms were largely confined to the York River. In recent years, however, heavy blooms have been observed from the Rappahannock River south to the mouth of Chesapeake Bay and in the James, Lafayette and Elizabeth Rivers. Alexandrium monilatum is a common HAB species that historically has bloomed along the US southern Atlantic and Gulf coasts. Despite decades of water sampling and HAB monitoring by scientists in the region, A. monilatum was not reported in the mid-Atlantic since the mid-1960’s until a significant bloom event in the York River, VA in 2007 marked the re-emergence of this toxic species in Chesapeake Bay. This recent intensification of C. polykrikoides and A. monilatum bloom activity in Chesapeake Bay is cause for concern due to both ecological and economic impacts. During the past several years the blooms have been associated with local mass mortalities of oyster larvae grown for aquaculture and restoration projects, as well as VIMS research organisms exposed to natural water. Blooms demonstrate a clear population progression in the York River with peak cell concentrations of C. polykrikoides followed two to three weeks later with peak concentrations of A. monilatum. In addition, while A. monilatum populations were contained largely in and near the York River until 2011, more recently A. monilatum has been found in water samples throughout southern Chesapeake Bay, and in mid-Atlantic coastal waters. Laboratory bioassays exposing larval fish and shellfish to field-collected bloom samples and to clonal isolate culture whole cell and lysate material have clearly demonstrated acute toxicity associated with these Chesapeake Bay HAB organisms. Sediment surveys are being done to map A. monilatum and C. polykrikoides cyst beds to more accurately predict the spatial distribution of blooms and identify initiation sites.