Geology topics

James E. Cloern

Publications and source records attributed to James E. Cloern.

80 records · Page 5Linked to original sources

USGS1982

Does the benthos control phytoplankton biomass in South San Francisco Bay?

South San Francisco Bay, USA, is a shallow coastal embayment that receives large inputs of nutrients (N. P, Si) and small local inputs of freshwater. Phytoplankton dynamics are typically characterized by a spring bloom when surface chlorophyll a increases from < 5 to > 40 mg m -3 . The bloom persists for 2 to 4 wk, and then dissipates. Phytoplankton biomass remains low (chlorophyll a < 5 mg m -3 ) from May through December, although light and nutrient availability are sufficient to sustain growth rates of 1 to 1.5 divisions d -1 in the expansive shallows. Transport processes apparently exert a small influence on phytoplankton biomass, and calculated zooplankton grazing accounts for only a small reduction in net rate of phytoplankton population growth in the shallows. However, suspension-feeding bivalves are sufficiently abundant to filter a volume equivalent to the volume of South Bay at least once daily. These observations suggest that grazing by benthos is the primary mechanism controlling phytoplankton biomass during summer and fall.

California↗

USGS1981

Plankton studies in San Francisco Bay; II, Phytoplankton abundance and species composition, July 1977-December 1979

Data are presented on the phytoplankton species composition and abundance in San Francisco Bay from July 1977 through December 1979. Phytoplankton identification and enumerations were made at selected stations. Sample collections were made at selected stations in the main channel of the Bay from Rio Vista on the Sacramento River to Calaveras Point in South San Francisco Bay, and at shoal stations in the central portion of South San Francisco Bay, San Pablo Bay, and Suisun Bay. Also reported, from October 1978 through December 1979, are the calculated phytoplankton carbon and percent nondiatom carbon, and the species list. This study is one component of an ongoing interdisciplinary study of San Francisco Bay. (USGS)

California↗

USGS1979

Phytoplankton ecology of the San Francisco Bay system -the status of our current understanding

No abstract available.

California↗

USGS1978

Simulation model of Cryptomonas ovata population dynamics in southern Kootenay Lake, British Columbia

A one-dimensional transient model is developed to simulate observed population dynamics of a small flagellate ( Cryptomonas ovata ) in southern Kootenay Lake, B.C., during a 1-year period (1 June 1974-31 May 1975). The model considers advective displacement of C. ovata as water flows from its southern entrance into the lake and moves northward toward sampling sites. Specific growth rate is computed from an experimentally determined function of mean irradiance, water temperature, and nutrient (ammonium and phosphate) concentration in the upper 10 m of the water column. Cell losses are assumed to result from zooplankton grazing and inhibition due to presence of the blue-green alga Anabaena . The model simulates well the timing and magnitude of all observed population changes and, more importantly, it gives insight into the important mechanisms which regulate population density of C. ovata in this natural system.

British Columbia↗

USGS1978

Empirical model of Skeletonema costatum photosynthetic rate, with applications in the San Francisco Bay estuary

An empirical model of Skeletonema costatum photosynthetic rate is developed and fit to measurements of photosynthesis selected from the literature. Because the model acknowledges existence of: 1) a light-temperature interaction (by allowing optimum irradiance to vary with temperature), 2) light inhibition, 3) temperature inhibition, and 4) a salinity effect, it accurately estimates photosynthetic rates measured over a wide range of temperature, light intensity, and salinity. Integration of predicted instantaneous rate of photosynthesis with time and depth yields daily net carbon assimilation (pg C cell −1 day −1 ) in a mixed layer of specified depth, when salinity, temperature, daily irradiance and extinction coefficient are known. The assumption of constant carbon quota (pg C cell −1 ) allows for prediction of mean specific growth rate (day −1 ), which can be used in numerical models of Skeletonema costatum population dynamics. Application of the model to northern San Francisco Bay clearly demonstrates the limitation of growth by low light availability, and suggests that large population densities of S. costatum observed during summer months are not the result of active growth in the central deep channels (where growth rates are consistently predicted to be negative). But predicted growth rates in the lateral shallows are positive during summer and fall, thus offering a testable hypothesis that shoals are the only sites of active population growth by S. costatum (and perhaps other neritic diatoms) in the northern reach of San Francisco Bay.

California↗

USGS1978

A von Bertalanffy growth model with a seasonally varying coefficient

The von Bertalanffy model of body growth is inappropriate for organisms whose growth is restricted to a seasonal period because it assumes that growth rate is invariant with time. Incorporation of a time-varying coefficient significantly improves the capability of the von Bertalanffy equation to describe changing body size of both the bivalve mollusc Macoma balthica in San Francisco Bay and the flathead sole, Hippoglossoides elassodon , in Washington state. This simple modification of the von Bertalanffy model should offer improved predictions of body growth for a variety of other aquatic animals.

Journal of the Fisheries Research Board of Canada↗

USGS1976

Recent limnological changes in southern Kootenay Lake, British Columbia

n response to a significant abatement of phosphate loading and the construction of a dam on its major inflow (the Kootenay River), southern Kootenay Lake experienced a number of limnological changes between 1969 and 1974. Water temperatures in 1974–1975 were similar to those previously reported for 1966–1969. However, water transparency has increased, particularly during the spring months.Nitrate concentrations have remained unchanged since 1969, and ranged from 2 to 8&ensp;μ M between 6 June 1974 and 22 May 1975. However, ammonium levels have been reduced in the winter months when mean concentration was about 1&ensp;μ M . Dissolved phosphorus levels in 1966–1969 were consistently around 3&ensp;μ M , but never reached 1&ensp;μ M in 1974. Phytoplankton populations in 1974–1975 (measured as chlorophyll a ) were lower than those during the 1966–1969 period, and evidence is presented that suggests that major shifts have occurred in the species composition of the phytoplankton. Whereas Kootenay Lake experienced blue–green and green algal blooms during the 1960's, no such phenomena were observed in 1974–1975 when the plankton was dominated by diatoms. Population maxima of the three most common zooplankters ( Cyclops bicuspidatus , Diaptomus ashlandi , and Diaphanosoma leuchtenbergianum ) have increased since 1966–1969.

British Columbia↗

USGS1976

The survival of coho salmon (Oncorhynchus kisutch) eggs in two Wisconsin tributaries of Lake Michigan

Natural reproduction of coho salmon (Oncorhynchus kisutch) in two Wisconsin tributaries of Lake Michigan (Little Scarboro Creek, Kewaunee Co., and Fischer Creek, Manitowoc Co.), is limited by an unusually high mortality of eggs and preemergent embryos. Of approximately 1800 coho salmon eggs planted in six study redds (spawning beds) within Fischer Creek (November 1972), none survived to hatching. The 1500 eggs planted in five study redds within Little Scarboro Creek produced 21 sac fry. The bottom materials of both streams are comprised of at least 15% (by volume) particles smaller than 0.84 mm in diam. Streambed gravels containing this quantity of sand, silt and clay do not allow for intragravel water of sufficient dissolved oxygen concentration or velocity to meet the oxygen requirements of developing salmon eggs. Water surrounding eggs planted in Fischer Creek and Little Scarboro Creek had mean dissolved oxygen concentrations of 3.96 and 6.22 mg/liter, respectively. The extremely low mean (2.83 C and 2.67 C) water temperatures of Fischer Creek and Little Scarboro Creek were an added cause of egg loss. In response to low temperature, planted eggs hatched after a prolonged development period of approximately 145 days. Gravel shifts caused by variable stream flow in Fischer Creek may also be responsible for killing naturally deposited eggs there

Wisconsin↗