Phytoplankton Patterns in Massachusetts Bay—1992–2007

Abstract

The Massachusetts Water Resources Authority (MWRA) conducts a comprehensive multidisciplinary monitoring program in Massachusetts Bay, Cape Cod Bay, and Boston Harbor to assess the environmental effects of a relocated secondary-treated effluent outfall. Through 2007, 8.7 years of baseline data and 7.3 years of postdiversion data (16 total years), including species level estimates of phytoplankton and zooplankton abundance, have been collected. MWRA's monitoring program and other studies make this region one of the most thoroughly studied and well-described marine systems in the world. The data show that the diversion of MWRA effluent from the harbor to the bay has decreased nutrients concentrations and improved water quality in the harbor (e.g., higher dissolved oxygen, lower chlorophyll). The diversion also resulted in an increase in dissolved inorganic nutrients (especially ammonium) in the vicinity of the bay outfall, but no obvious impacts such as increased biomass or decreased bottom water dissolved oxygen have been observed. Regional changes in phytoplankton and zooplankton unrelated to the diversion have been seen, and it is clear that the bays are closely connected both physically and ecologically with the greater Gulf of Maine. Direct responses to modifications of the nutrient field within a 10×10-km area centered near the midpoint of the 2-km long outfall diffuser in Massachusetts Bay (a.k.a. the nearfield) have not been seen in the plankton community. However, plankton variability in the bays has been linked to large regional to hemispheric scale (NAO) processes.

Patterns and Scales of Phytoplankton Variability in Estuarine–Coastal Ecosystems

“…For example, a trend of declining phytoplankton abundance in the Gulf of Naples occurred during a period of increasing winter cloudiness and intensification of winds (Zingone et al 2009). Phytoplankton biomass declined in Narragansett Bay (Borkman and Smayda 2009) and nearby Massachusetts Bay (Keller et al 2001;Hunt et al 2009) after the North Atlantic Oscillation index shifted from negative to positive. The mechanism appears to be earlier winter warming and control of phytoplankton growth by copepods during the positive phase of the North Atlantic Oscillation.…”

Variability of Winter-Spring Bloom Phaeocystis pouchetii Abundance in Massachusetts Bay

“…At the laboratory, the seawater samples were prepared for analysis by concentrating the sample by gravitational settling as described by Borkman (1994) which is similar to the methods of Hasle (1959), Iriarte and Fryxell (1995), and Sukhanova (1978). Phytoplankton analyses were performed as described by Hunt et al (2010).…”

“…Members of the marine prymnesiophyte phytoplankton genus Phaeocystis are a regular component of the winter-spring phytoplankton community of north-temperate coastal seas (Cadee and Hegeman 2002;Schoemann et al 2005), and this includes blooms of Phaeocystis pouchetii (Hariot, Lagerheim) in the Gulf of Maine (Bigelow 1926;Hunt et al 2010). The ability of Phaeocystis to form high biomass blooms (>10 mg C L −1 ; up to 200×10 6 cells L −1 ; Schoemann et al 2005) which sequester a large portion of ecosystem resources and alter trophic pathways (Tang et al 2001) make Phaeocystis one of the few "keystone" phytoplankton taxa whose blooms significantly alter ecosystem function (Lancelot et al 1994;Verity and Smetacek 1996;Verity et al 2007a) via modification of biogeochemical cycling (Smith et al 1991;Stefels et al 1995) and alteration of food web structure (Rousseau et al 2000).…”

“…Communicated by Hans W. Paerl The Massachusetts Bay and Cape Cod Bay regions of the Gulf of Maine have long been known for their particularly "rich Phaeocystis blooms" (Bigelow 1926) with blooms of P. pouchetii often occurring there during late winter and early spring. Recent data suggests that there is considerable annual variability in the magnitude of Phaeocystis blooms in the Massachusetts Bay region of the Gulf of Maine (Hunt et al 2010). For example, during 1992For example, during -2007, regular monitoring showed that Phaeocystis was absent from Massachusetts Bay during 1993Bay during , 1995Bay during , 1996Bay during , 1998Bay during , and 1999 followed by a shift to elevated abundance during -2005(Hunt et al 2010.…”

“…Recent data suggests that there is considerable annual variability in the magnitude of Phaeocystis blooms in the Massachusetts Bay region of the Gulf of Maine (Hunt et al 2010). For example, during 1992For example, during -2007, regular monitoring showed that Phaeocystis was absent from Massachusetts Bay during 1993Bay during , 1995Bay during , 1996Bay during , 1998Bay during , and 1999 followed by a shift to elevated abundance during -2005(Hunt et al 2010. Why Phaeocystis occurs in relatively high abundance during some years and not others is not well understood.…”