For the past 4 summers (1985–1988), the microalga Aureococcus anophagefferens bloomed in Long Island embayments, causing large scale perturbations in water column dynamics. The “brown tide” algal blooms brought about significant changes in the benthic community as well. The high cell densities (>109 l-1) of A. anophagefferens significantly increased light absorption in the water column (Cosper et al., 1987), and reduced the light available to plants living on the bottom of the embayments.

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The first appearance of the “brown tide” in the early summer of 1985 was over a wide geographic range along the northeast coast of the United States in non-contiguous bodies of water: Narragansett Bay, Rhode Island, and Long Island embayments in New York as well as Barnegat Bay in New Jersey (Fig.1) (Nuzzi and Waters, 1989; Olsen, 1989; Sieburth et al., 1988; Sieburth and Johnson, 1989; Smayda and Villareal, 1989).

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Water motion effects on metabolism of a common reef-building coral, Acropora formosa Dana, were studied utilizing laboratory incubations. Net photosynthesis and respiration were significantly reduced (≈ 25% lower) in unstirred conditions compared with stirred conditions. Dark calcification was reduced by ≈60% in unstirred conditions. Light-enhanced calcification appeared to be reduced by ≈ 25% in unstirred conditions; however, this effect was not statistically significant.

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The relationships between light regime, photosynthesis, growth and depth distribution of a temperate seagrass, Zostera marina L. (eelgrass), were investigated in a subtidal eelgrass meadow near Woods Hole, MA. The seasonal light patterns in which the quantum irradiance exceeded the light compensation point (Hcomp) and light saturation point (Hsat) for eelgrass photosynthesis were determined.

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The interaction of sediment ammonium (NH+4) availability and eelgrass (Zostera marina L.) growth, biomass and photosynthesis was investigated using controlled environment and in-situ manipulations of pore water ammonium concentrations. Sediment diffusers were used to create pore water diffusion gradients to fertilize and deplete ammonium levels in sediments with intact eelgrass rhizospheres.

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The short-term temperature responses of the photosynthesis-irradiance (P-I) relationships and respiration of Zostera marina L. (eelgrass) leaves were determined at eight temperatures from 0 to 35°C for plants growing at 20–22°C in Great Harbor, Woods Hole, Massachusetts.

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Photosynthetic and growth responses were assessed in Zostera marina L. transplants within and beyond the natural extent of an eelgrass meadow in Great Harbor, Woods Hole, MA. Transplant survival and rapid growth inshore of the shallow edge of the meadow (0.5 and 0.8 m water depth) indicated a periodic disturbance factor maintaining the shallow edge of the meadow.

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ABSTRACT: Photosynthesis, biomass and growth characteristics of the temperate seagrass, Zostera marina L. (eelgrass), were examined in a meadow in Great Harbor, Woods Hole, Massachusetts during June and August, 1982. Underwater lamps and light shading screens were placed at shallow (1.3 m) and deep (5.5 m) stations to lengthen and shorten daily light periods.

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The adaptive physiology of Zostera marina, L. (eelgrass) was investigated along a water depth gradient in order to assess the interactions of this prolific temperate seagrass with its environment. In situ and controlled-environment manipulations of light and sediment availability along with transplants beyond and within the eelgrass meadow were conducted.

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Role of Seagrass Photosynthesis in Root Aerobic Processes

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