Water column

About: Water column is a research topic. Over the lifetime, 13706 publications have been published within this topic receiving 496626 citations.

Sea-ice algae: Major contributors to primary production and algal biomass in the Chukchi and Beaufort Seas during May/June 2002

Abstract: Sea-ice and water samples were collected at 14 stations on the shelves and slope regions of the Chukchi and Beaufort Seas during the spring 2002 expedition as part of the Shelf–Basin Interaction Studies. Algal pigment content, particulate organic carbon and nitrogen, and primary productivity were estimated for both habitats based on ice cores, brine collection and water samples from 5-m depth. The pigment content (0.2–304.3 mg pigments m −2 ) and primary productivity (0.1–23.0 mg C m −3 h −1 ) of the sea-ice algae significantly exceeded water-column parameters (0.2 and 1.0 mg pigments m −3 ; −3 h −1 ), making sea ice the habitat with the highest food availability for herbivores in early spring in the Chukchi and Beaufort Seas. Stable isotope signatures for ice and water samples did not differ significantly for δ 15 N, but for δ 13 C (ice: −25.1‰ to −14.2‰; water: −26.1‰ to −22.4‰). The analysis of nutrient concentrations and the pulse-amplitude-modulated fluorescence signal of ice algae and phytoplankton indicate that nutrients were the prime limiting factor for sea-ice algal productivity. The estimated spring primary production of about 1–2 g C m −2 of sea-ice algae on the shelves requires the use of substantial nutrient reservoirs from the water column.

Seasonality in East Africa's coastal waters

Abstract: A review of existing literature and data on seasonal patterns in East Africa's coastal waters indicates distinct seasonality in physical, chemical and biological oceanographic parameters. Seasonal patterns are dictated by the behavior of the Inter-Tropical Convergence Zone (ITCZ) which creates 2 distinct seasons the northeast and southeast monsoons. SE monsoon (March to October) meteorological parameters are characterized by high cloud cover, rainfall, river discharge, terrestrial runoff and wind energy while solar insolation and temperatures are low; SE monsoon oceanographic parameters are characterized by cool water, a deep thermocline, high water-column mixing and wave energy, fast currents, low s a h ~ t y and high phosphorus. These parameters are reversed during the NE monsoon. Nitrogen availability and planktonic primary productivity are high along the Somali coast and estuarine and river discharge areas during the southeast monsoons due to nutrient upwelling and terrestrial runoff. In near-shore waters off Tanzania, nitrogen fixation is the major source of nitrogen and is highest during NE monsoons when the water column is stable. Coral reef benthic algal biomass and diversity is greatest during the SE monsoons. Fish catch and reproduction are highest during NE monsoons in Kenya and Tanzania. Transition periods between monsoons may also be important times in determining productivity and reproduction.

Influence of Eastern Oysters on Nitrogen and Phosphorus Regeneration in Chesapeake Bay, USA

Abstract: Suspension-feeding bivalves couple pelagic and benthic processes because they consume seston from the water column, and their biodeposits (feces and pseudofeces) settle on the sediment surface. Abundant stocks of bivalves can exert grazer control on phytoplankton, and this results in some nitrogen and phosphorus being regenerated to the water column as excreta and via microbial decomposition of biodeposits. Bivalve biodeposition, however, enhances net ecosystem losses of N and P via sediment burial and bacterially mediated, coupled nitrification-denitrification. Bivalve feeding also reduces turbidity and thereby increases light available for microphytobenthos. Although microphytobenthos may compete with nitrifying bacteria for N, potentially reducing coupled nitrification-denitrification, they retain N and P within sediments, further reducing net regeneration to the water column.