Plankton studies in Buzzards Bay, Massachusetts, USA III. Dmoflagellates, 1987 to 1988

Abstract

Dinoflagellates were counted and identified in >20 v samples from Buzzards Bay, Massachusetts, USA, from October 1987 to September 1988. Eight stations were sampled at monthly or twice-monthly intervals. Dinoflagellates were the most abundant organisms in the >20 pm microplankton samples (excluding diatoms), comprising up to 99% of total organisms. A total of 46 dinoflagellate species from 19 genera were recorded, and there were dinoflagellate blooms throughout the year. Bloom-forming taxa included Gymnodinium sanguineurn, Heterocapsa triquetra, Prorocentrum minimum, and Prorocentrum triestinum. Mean annual dinoflagellate abundance was 9.7 X 103 cells I-', but blooms reached concentrations of 10' cells 1-'. Dinoflagellates were most abundant from spring to fall, and dinoflagellate blooms developed in between diatom blooms, coinciding with increasing silicate concentrations. This suggests that after silicate depletion by diatom blooms, dinoflagellates were able to exploit an undersaturated phytoplankton niche. Dinoflagellates were much more abundant at the New Bedford sewage outfall and in New Bedford Harbor than in the rest of the bay. The effect of concentrating dinoflagellate samples with a 20 pm mesh screen was examined by comparisons of abundance of selected taxa in screened and unscreened whole-water samples concentrated by sedimentation. There were no significant differences between screened and whole-water samples (2-way ANOVA for paired comparisons) for total dinoflagellates, or for 5 abundant taxa.

Plankton studies in Buzzards Bay, Massachusetts, USA. VI. Phytoplankton and water quality, 1987 to 1998

“…These include studies of phytoplankton pigments and nutrients , hydrography and bacterioplankton , phytoplankton abundance and composition , Borkman 1994, Pierce & Turner 1994a, Turner et al 1995, phytoplankton primary production (Hill 1998), tintinnid and ciliate abundance and composition (Pierce & Turner 1994b), ichthyoplankton abundance, composition and growth (Chute & Turner 2001, Gauthier et al 2008), and copepod feeding (Nakamura & Turner 1997) However, an overview of long-term trends and patterns in temperature, hydrography, water clarity, nutrient concentrations and phytoplankton abundance and community composition has not previously been presented.…”

“…Although this dinoflagellate is well-known for causing red tides and shellfish toxicity in coastal waters of New England (Anderson 1997), surprisingly it had never been previously recorded to bloom in Buzzards Bay, likely because there had been no phytoplankton abundance and community composition monitoring in Buzzards Bay prior to the onset of our monitoring program in 1987. Pierce & Turner (1994a) and Turner et al (1995) reported that A. fundyense was a recurrent component of the phytoplankton of Buzzards Bay from June to October 1988. Although it was found at all stations, it was more typical of the northern area and the Cape Cod Canal.…”

“…Although we took 11 yr (1987 to 1998) of concurrently collected monthly nutrient and phytoplankton samples, these had been previously analyzed for community composition only for 1987-88 , Borkman 1994, Pierce & Turner 1994a, Turner et al 1995. Thus, we examined selected archived phytoplankton samples from 1987 to 1998 for community composition and abundance.…”

“…As water quality deteriorates, certain 'nuisance' taxa may be expected to flourish. Conversely, if water quality improves, and conditions near the New Bedford sewage outfall indicate that it has, then the phytoplankton community might be expected to also reflect such changes.Although we took 11 yr (1987 to 1998) of concurrently collected monthly nutrient and phytoplankton samples, these had been previously analyzed for community composition only for 1987-88 (Borkman et al 1993, Borkman 1994, Pierce & Turner 1994a, Turner et al 1995. Thus, we examined selected archived phytoplankton samples from 1987 to 1998 for community composition and abundance.…”

“…in late August-early September. This bloom followed a period of silicate build-up in June and July, after depletion of silicate in the spring.We also made the first recording of a bloom of Alexandrium fundyense (formerly Gonyaulax tamarensis and Alexandrium tamarense; see Anderson et al 2005) in Buzzards Bay in summer 1988 (Pierce & Turner 1994a, Turner et al 1995. Although this dinoflagellate is well-known for causing red tides and shellfish toxicity in coastal waters of New England (Anderson 1997), surprisingly it had never been previously recorded to bloom in Buzzards Bay, likely because there had been no phytoplankton abundance and community composition monitoring in Buzzards Bay prior to the onset of our monitoring program in 1987.…”