The Economics of Conjunctive Groundwater Management with Stochastic Surface Supplies

Groundwater management with stochastic surface flows and artificial recharge is considered. Theoretical analysis characterizes the decision rules and establishes conditions for convergence of socially optimal and common property withdrawals and pumping lifts to limiting probability distributions. An empirical application to Kern County, California finds that optimal withdrawals are generally increasing in hydraulic head and decreasing in surface flows; however, nonmonotone behavior is observed in some instances. Artificial recharge is not observed in the limiting distribution due to an interaction of several factors. Optimal management implies relatively small gains over unregulated groundwater use when preferences are risk neutral.     

Electrophoretic variants of egg white transferrin indicate a low rate of intraspecific brood parasitism in colonial cliff swallows in the Sierra Nevada,California

Summary The frequency of intraspecific brood parasitism in two colonies of cliff swallows (Hirundo pyrrhonota) nesting in the eastern Sierra Nevada in California was assessed through an electrophoretic analysis of egg white (albumin) proteins. Albumin proteins are maternally derived and are presumed to directly reflect maternal genotype. Thus, a comparison of protein banding patterns produced by eggs collected from a single clutch allows any egg laid by a female other than the putative mother to be detected. Eggs were collected from 13 cliff swallow nests in 1984 and 41 nests in 1987, a total of 54 nests. Of the clutches collected in 1984, one showed evidence of intraspecific brood parasitism, giving a nest parasitism rate of 7.6%. In 1987, one of 41 nests contained a parasitic egg, for a parasitism rate of 2.4%. Over both years combined the rate of intraspecific brood parasitism was 2 of 54 nests, or 3.7%. These parasitism rates are much lower than those estimated for Nebraskan cliff swallows (22–43%) and 2nd-year purple martins (36%). Possible explanations for the discrepancy between parasitism rates in Sierran cliff swallows and other groups of swallows are discussed.Correspondence to: A.P. Smyth     

Productivity of bacteria and microalgae and the effect of grazing by holothurians in sediments on a coral reef flat

Bacterial productivity in sandy sediments on reef flats at Lizard Island, Great Barrier Reef was determined from the rate of incorporation of tritiated thymidine into DNA. The study was conducted during January 1982 and July 1983. A small diurnal increase occurred in sediments having a dense population of microalgae. Bacterial production was 120 to 370 mg C m^-2 d^-1 in summer on reef flats, which was equivalent to 30–40% of primary production by benthic microalgae. In winter, rates of primary production by benthic microalgae and secondary production by bacteria were about one-half to one-fifth of those in summer. There was much variation in production, due to patchiness in the distribution of benthic microbes, especially microalgae. Doubling times for the bacteria in surface sediment were 1 to 2 d in summer and 4 to 16 d in winter on the reef flats. These high productivity values for bacteria indicated that a net input of organic matter to the sediment was needed to support the growth of bacteria. Sediment bacteria thus have a very important role in transforming organic matter on the reef flats. Grazing by Holothuria atra depressed both primary production and bacterial production. It was estimated that these holothurians ate about 10 to 40% of bacterial carbon produced each day in summer, and thus have an important role in the carbon cycle. Harpacticoid copepods were numerically important components of the benthic meiofaunal community and probably had a significant impact on bacterial density as grazers.     

Role of herbivory in controlling phytoplankton abundance: annual pigment budget for a temperate marine fjord

An annual pigment budget was constructed for Dabob Bay, Washington (USA) by comparing the downward vertical loss of phytoplankton pigments (chlorophyll and pheopigments) to the production of chlorophyll within the euphotic zone. The vertical flux of pigments was measured with sediment traps deployed at intervals of 1 to 6 wk over a 2.5 yr period yielding 763 d of trap exposure (28 November 1978–16 June 1981). The production rate of chlorophyll was calculated from measurements of algal specific growth rates, chlorophyll (chl) crops, primary production (as carbon) and appropriate C: chl ratios. Sixty one to 77% of the annual chlorophyll production was accounted for by the vertical flux of pheopigments resulting from herbivorous zooplankton grazing (macrozooplankton). Algal sinking, represented by downward chlorophyll flux, accounted for only 5 to 6% of the annual chlorophyll production. The remaining fraction of chlorophyll production was estimated to be consumed by small herbivores (microzooplankton), whose fecal material contributes to the suspended pool of pheopigments found in the euphotic zone. The suspended pheopigments are continuously removed by photodegradation. In Dabob Bay, the major process controlling phytoplankton abundance is zooplankton grazing and it appears that the ultimate fate of most phytoplankton is to be consumed by herbivores.     

Carbon fixation in marine phytoplankton: carboxylase activities and stable carbon-isotope ratios; physiological and paleoclimatological aspects

We measured the activity of three carboxylases: RuBP carboxylase, PEP carboxylase and PEP carboxykinase of marine phytoplankton species in culture and in natural communities. Activities of the three carboxylases were measured simultaneously with stable carbon-isotope ratios. The enzymatic activities have been used to estimate the importance of carboxylation and its impact on the ¹³C:¹²C ratio (expressed as ¹³C). The marine phytoplankton species in culture were Fragilariopsis kerguelensis, Nitzschia turgiduloides, Skeletonema costatum, Phaeodactylum tricornutum, Isochrysis galbana, Dunaliella marina, and Prorocentrum micans, and the field samples were collected from different depths off the coast of Portugal (August/September, 1981). Our results indicate that, as in terrestrial plants, the ¹³C value is a good indicator of the extent of carboxylation. RuBP carboxylase activity was always predominant, whereas the ¹³C value never reached values typical of the C₄ pathway. The carboxylases could be PEP carboxylase (in dinoflagellates) or PEP carboxykinase (in diatoms). carboxylation increased at the end of the exponential growth phase in a diatom culture and with increased biomass in natural samples. We interpret these increases as an adaptative response mechanism to poor environmental conditions, especially to low light intensity.     

Suspected mechano- and chemosensory structures of Temora longicornis (Copepoda: Calanoida)

The antennulary (A1) setae of Temora longicornis Müller are suspected of being mechanosensory. In the present study, the fine structure of the antennule, setae and pegs was examined by scanning and transmission electron microscopy. Two setae arise proximal to each antennule segment junction. The supraaxial (Type 1) seta of each pair is innervated by a pair of ciliary dendrites and has the morphological characteristics of a mechanoreceptor. The sub-axial (Type 2) seta may be chemosensory, and is innervated by a varying number of dendrites, but always more than two. The antennulary pegs do not appear to be innervated. T. longicornis is directionally sensitive to water disturbances, and this is consistent with the physical structure of the setae. Integumental structures on the body and other non-feeding appendages are described. These observations support previous behavioural experiments which suggested the antennule to be the major site for mechanoreception in copepods; however, mechanoreceptors must also occur on other parts of the body.     

Timing of hatching inAmmodytes marinus from Shetland waters and its significance to early growth and survivorship

The significance of hatch date for the growth and survival of the sandeel,Ammodytes marinus, was investigated using otolith microstructure. Hatch dates of 2 to 6 mo-old juvenileA. marinus caught near Shetland were compared between 1990 and 1992, during which period year-class strength varied by more than an order of magnitude. The hatch-date distribution of juveniles in the 1992 year-class was compared with that estimated directly from the abundance of newly emerged larvae on the spawning grounds. The extent of larval hatching periods in 1990 and 1991 was also estimated from continuous plankton-recorder data. There were significant differences in hatching periods between all three years, hatching in 1990 and 1992 being markedly earlier than the long-term mean peak in hatching indicated from archival data. Most individuals from the 1991 year-class attained a larger size by July than those in other year-classes, despite hatching later. Variation in individual growth rates both within and between year-classes indicated that there was a seasonal cycle of growth opportunity in all years investigated. The study suggests that the degree of coupling between hatching and the onset of spring secondary production may be an important contributory factor to year-class variability in this species.     

Demography and phenology of the intertidal green algaCodium setchellii: The enigma of local scarcity on sand-influenced rocky shores

Demographic and phenological attributes that characterize rare and scarce species have not been extensively investigated for marine benthic organisms. From 1984 to 1987, 1 investigated the population ecology of the low intertidal, psammophytic green algaCodium setchellii Gardner that forms low-density populations on sand-influenced rocky benches on N.E. Pacific shores. To address why the alga is not more common in the habitat in which it is most abundant, I quantified sand fluctuations and population dynamics ofC. setchellii at several sites along the central coast of Oregon, USA. Sand movement was highly unpredictable both spatially and temporally on a local scale. AlthoughC. setchellii became fertile in late autumn to winter, the alga and rocky surfaces were often deeply buried by sand in these seasons. Algal recruitment was also spatially and temporally variable, and mortality of small thalli was high. Thallus growth was generally slow, and the alga had the capacity to persist at a given size for long periods. On sand-influenced rocky shores, mortality of largethalli was low, with some thalli persisting for several years. In laboratory experiments,C. setchellii lost substantial biomass during 4 to 5 wk sand burials, whereas two sympatric species of psammophytic algae lost little to no biomass. The within-site scarcity ofC. setchellii may be a consequence of (1) largely unpredictable environmental conditions that reduce algal recruitment and survival, and (2) apparent lack of specialized anatomical or reproductive adaptations to persist on sand-scoured rocky shores. The alga's persistence may be due to its slow growth and long lifespan.     

A correlative study on liver glycogen and endosulfan toxicity in Heteropneustes fossilis (Bloch.)

The biochemical tests were conducted to find out the relationship between liver glycogen and endosulfan toxicity on a catfish, Heteropneustes fossilis (Bloch.) using 0.00075, 0.00050 and 0.000375 ppm concentrations for 15, 30, 45 and 60 days of exposure periods. The quantity of liver glycogen showed decreasing trend as concentration of toxicant increased. The depletion in glycogen contents is greatly affiliated to cellular damage in hepatic cells.     

Self-fertilization and maternal enzymes in the planulae of the coral Goniastrea favulus

Electrophoretic analysis of planulae obtained from controlled breeding experiments with the coral Goniastrea favulus during spawning events in 1986 and 1987 on the Great Barrier Reef, Australia, shows that offspring are produced equally frequently by outcrossing or self-fertilization, leading to a genetically determined rate of selfing of around 50%. Field rates of selfing may be greater than this as a consequence of the limited dispersal of gametes within this species. However, the level of heterozygote depression found in one population is well below that which would be predicted for such levels of selfing. In one enzyme system, glucosephosphate isomerase, the maternal phenotype continues to be expressed in the planula larva for between 11 and 17 d after fertilization. This effect is postulated to result from a residual of maternal enzyme and RNA derived from a relatively large egg.