The high spatial variability of estuaries poses a challenge for characterizing estuarine water quality. This problem was examined by conducting monthly high-resolution transects for several water quality variables (chlorophyll a, suspended particulate matter and salinity) in San Francisco Bay (California, U.S.A.). Using these data, six different ways of choosing station locations along a transect, in order to estimate mean conditions, were compared. In addition, 11 approaches to estimating the variance of the transect mean when stations are equally spaced were compared, and the relationship between variance of the estimated transect mean and number of stations was determined. The results provide guidelines for sampling along the axis of an estuary: (1) choose as many equally-spaced stations as practical; (2) estimate the variance of the meanyby var (y)=(1/10n2)Σnj=2(yj−yj−1)2, wherey1, . . .,ynare the measurements at thenstations; and (3) attain the desired precision by adjusting the number of stations according to var(y)α1/n2. The inverse power of 2 in the last step is a consequence of the underlying spatial correlation structure in San Francisco Bay; more studies of spatial structure at other estuaries are needed to determine the generality of this relationship.

As part of a pilot regional monitoring program, water samples were collected in the San Francisco Bay estuary during 22 cruises from January through October 1995.Conductivity, temperature, light attenuation, turbidity, oxygen, and in-vivo chlorophyll a fluorescence or absorbance were measured longitudinally and vertically in the main channel of the estuary from south of the Dumbarton Bridge in the southern part of the Bay to Rio Vista on the Sacramento River.Discrete water samples were analyzed for chlorophyll a, phaeopigments, suspended particulate matter, and dissolved oxygen.Water density was calculated from salinity, temperature, and pressure (depth), and is included in the data summaries.Phytoplankton species abundance and cell volume were determined at selected stations every other month.

Water samples were collected in the San Francisco Bay estuary during 22 cruises from January through December 1993. Conductivity, temperature, light attenuation, turbidity, oxygen, and in-vivo fluorescence were measured 1ongitudinally and vertically in the main channel of the estuary from south of the Dumbarton Bridge in the southern part of the bay to Rio Vista on the Sacramento River. Discrete water samples were analyzed for chlorophyll a, phaeopigments, suspended particulate matter, and dissolved oxygen. Water density was calculated from values for salinity, temperature, and pressure (depth), and is included in the data summaries. Photosynthetic parameters, water column respiration, and phytoplankton species abundance and cell volume were determined at selected stations every other month.

Water samples were collected in the San Francisco Bay estuary during 22 cruises from January through December, 1991.Conductivity, temperature, light attenuation (turbidity), and in-vivo fluorescence were measured longitudinally and vertically in the main channel of the estuary from near the Dumbarton Bridge in the southern part of the bay to Rio Vista on the Sacramento River.Discrete water samples were analyzed for chlorophyll a and phaeophytin.Water density was calculated from values for salinity, temperature, and pressure (depth), and is included in the data summaries.

Water samples were collected in the San Francisco Bay estuary during 35 cruises from January through December, 1992.Conductivity, temperature, light attenuation (turbidity), and in-vivo fluorescence were measured longitudinally and vertically in the main channel of the estuary from near the Dumbarton Bridge in the southern part of the bay to Rio Vista on the Sacramento River.Discrete water samples were analyzed for chlorophyll a and phaeopigments.Water density was calculated from values for salinity, temperature, and pressure (depth), and is included in the data summaries.

A flume system and protocol for measuring the filtration rate of infaunal bivalves is described. Assemblages of multi-sized clams, at natural densities and in normal filter-feeding positions, removed phytoplankton suspended in a unidirectional flow of water. The free-stream velocity and friction velocity of the flow, and bottom roughness height were similar to those in natural estuarine waters. Continuous variations in phytoplankton (Chroomonas salinay) cell density were used to measure the filtration rate of the suspension-feeding clam Potamocorbula amurensis for periods of 2 to 28 h. Filtration rates of P. amurensis varied from 100 to 580 liters (gd)-1 over a free-stream velocity range of 9 to 25 cm s-1. Phytoplankton loss rates were usually constant throughout the experiments. Our results suggest that suspension-feeding by infaunal bivalves is sensitive to flow velocity.

Water samples were collected in the San Francisco Bay estuary during 42 cruises from February, 1988, through December, 1989.Conductivity, temperature, light attenuation (turbidity), and in-vivo fluorescence were measured longitudinally and vertically in the main channel of the estuary from near the Dumbarton Bridge in the extreme southern part to Rio Vista on the Sacramento River.Discrete water samples were analyzed for chlorophyll a. Water density was calculated from values for salinity, temperature, and pressure (depth), and is included in the data summaries.

The Land‐Sea Interface (LSI) is a region of particular importance to human endeavor. The region includes the exposed outer coast, coastal waters, bays, estuaries, and deltas. Its area is small in comparison with that of the adjacent open ocean or land, but the LSI is at once a region of high biological productivity and complexity and the portion of the ocean most heavily impacted by human activities.The LSI also has a profound effect on the transport of materials between the land and the sea. Chemically reactive materials transported from the land to the sea undergo intense biogeochemical cycling and net transformations within the LSI. There are, for example, important sorption reactions associated with the transition from freshwater to saltwater. These reactions alter the distribution and bioavailibility of metals and may affect their toxicity and bioaccumulation.

The research was sponsored by NSF Grant Nos. OCE 85-00679 (awarded to SVS) and OCE 82-14837 (awarded to JTH).

Rates of phytoplankton productivity, respiration, and nutrient uptake and regeneration are presented. These observations were made on the Potomac River estuary (POTE) during four cruises between August 1977 and August 1978. Four experimental methods were used: carbon uptake using carbon-14, carbon uptake and respiration by a pH method, productivity and respiration by the dissolved oxygen method, and nutrient (NH4+, NO3-, NO2-, PO4=, and SiO2=) uptake and regeneration by colorimetry. The experiments were made at sites representative of conditions in four principal reaches of the tidal Potomac River estuary: near the mouth, seaward of the summer nutrient and phytoplankton maximum, near the region of maximum phytoplankton standing stock , and near the maximum anthropogenic nutrient source. (USGS)