Population Dynamics and Environmental Variability

Green, Roger H.

doi:10.1093/icb/9.2.393

Cited by 11 publications

(2 citation statements)

References 14 publications

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“…The resulting simple community will not be unstable a priori (Moore, 1977) since a number of stabilizing mechanisms may be in operation (Murdoch & Oaten, 1975). However, much of the enviroment variability in the Lynher estuary is erratic rather than predictable, so that the community structure (in the sense of Margalef, 1963) is destroyed 'because the predictability upon which evolution of genetically controlled patterns of growth, feeding and reproduction must be based is diminished' (Green, 1969). Lowered diversity and consequent instability of the food-web (MacArthur, 1955) w iU further enhance the population response to erratic environmental variability.…”

Section: Discussionmentioning

confidence: 99%

Temporal Variations in Annual Production and Biomass in Estuarine Populations of two Polychaetes, Nephtys Hombergi and Ampharete Acutifrons

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Warwick

1980

J. Mar. Biol. Ass.

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The annual production (P) and mean annual biomass (B) of two species of polychaete, Nephtys hombergi and Ampharete acutifrons, have been estimated over a 5-year period, from October 1972 to October 1977, in the estuary of the River Lynher, Cornwall. Fo£ Nephtys, P varied between 600 g dry wt.m~2 in 1973 and 2-84 g.m~2 in 1977, and B between 4-76 g.m"2 in 1976 and 3.21 g.m~2 in 1975. The PJB ratio varied between 1-42 in 1973 and o-8i in 1977. Over the period of study the P/B ratio gradually declined as a result of reduced recruitment which resulted in a higher proportion of older year-classes in the population. In Ampharete, P varied between 12-54 g-rn~2 in 1976 and 0-12 g.m" 2 in 1977 and B between 229 g. m~2 in 1976 and 0-03 g. m~2 in 1977, a much larger variation than in Nephtys. However, the P/B ratio was more stable than for Nephtys, varying between 5-47 in 1976 and 4-00 in 1977: because Ampharete is an annual species the P/B value is not dependent on the balance of year-class strengths as in Nephtys. The variability of these values is discussed in relation to the reproductive biology and longevity of the two species. INTRODUCTIONProduction rates and production/biomass ratios have been estimated for a large number of macrobenthic species (Hargrave, 1977;Robertson, 1979). The usefulness of such estimates is limited by a lack of information on their temporal and spatial stability; we are aware of only one study (Sarvala, 1980) in which production has been estimated for more than one year. The present study investigates the stability of the production (P), biomass (B) and P/B values of two polychaete species, Nephtys hombergi Savigny and Ampharete acutifrons (Grube), over a 5-year period.

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Section: Discussionmentioning

confidence: 99%

Temporal Variations in Annual Production and Biomass in Estuarine Populations of two Polychaetes, Nephtys Hombergi and Ampharete Acutifrons

Price

Warwick

1980

J. Mar. Biol. Ass.

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“…This variation often reflects the interaction of biotic and abiotic factors (CouU 1985;Holland 1985;Nichols 1985) and temporal shifts in numbers of species, abundance, diversity and species composition are characteristic of shallow-water benthic communities (Green 1969;Eagle 1975;McCall 1977;Watling 1975; Holland and Mountford 1977;Rachor and Gerlach 1978;Loi and Wilson 1979). Even though subtidal abundances in the 1986, were lower than in recent years, regression models, which included natural abiotic factors as variables, accounted for the lower values; thus the observed differences were not due to plant operation.…”

Section: Numbers Of Speciesmentioning

confidence: 99%

Monitoring the marine environment of Long Island Sound at Millstone Nuclear Power Station, Waterford, Connecticut : summary of studies prior to Unit 3 operation / [prepared by the Environmental Laboratory staff of Northeast Utilities Service Company].

1987

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Several programs were established to provide baseline data for assessing impacts of MNPS on fish assemblages. These include studies of planktonic, demersal, pelagic and shore-zone fish assemblages, and estimates of the number offish impinged and entrained. Plankton studies conducted since 1973 included collections of fish larvae at various stations, and entrainment mortality and thermal tolerance research on selected larval fish taxa. The trawl sampling program was established in 1973 to monitor spatial and temporal fluctuations of demersal fish. The gill net program, started in 1971 to provide qualitative estimates of local pelagic fish assemblages, was dropped at the end of 1982 because catches were generally low and none of the species collected were adversely affected by MNPS. The seine sampling program was established in 1969 to monitor shore-zone fish. Impingement monitoring began at MNPS Unit 1 in 1972 and at Unit 2 in September 1975 and was supplemented by several fish diversion and survival studies. These programs, which provide the data necessary for assessing the effects of two-unit operation also provide the baseline for three-unit impact assessment.Over 100 taxa of fish have been collected in the various Fish Ecology monitoring programs at MNPS from .January 1976 through December 1985. Composition of the fish assemblages studied during that period remained relatively stable and were typical of those reported for LIS by other researchers. Eight taxa were selected for detailed analyses based on their susceptibility to impact from impingement and entrainment: anchovies, sand lance, sticklebacks, silversides, tomcod, grubby, cunner and tautog.The abundance of these taxa varied both seasonally and annually in all programs and to separate fluctuations representing natural variability from those resulting from the construction and operation of MNPS, a time-series approach was developed and applied to the monitoring data. This approach, which combined several statistical techniques (harmonic regression, analysis of variance and time-series analysis) to summarize catch fluctuations in the long-term data series, provided confidence intervals that were narrower than those associated with annual or monthly means or medians and was, therefore, more sensitive to unusual abundance fluctuations.The abundances of potentially impacted taxa remained relatively stable throughout the 10-year period, except for larval and juvenile sand lance, and larval anchovy, cunner and tautog. Except for larval sand lance, these abundance changes were short-term. Larval sand lance abundance decreased during 1982 and has remained low since then. A mass impingement (390,000) of sand lance juveniles occurred in a one week period in .luly 1984 but was an uncommon event and is not expected to recur. 10In 1984, there was a marked decrease in the abundance of larval anchovy, cunner and tautog but this decrease was also observed in other parts of LIS. The reasons for this decline were not known but during this time ctenophores, a plankton pre...

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Zum überflutungsverhalten zwei‐ und dreiphasig betriebener Rührreaktoren

Wiedmann

1983

Chemie Ingenieur Technik

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The flooding behaviour of two-and three-phase operating stirred reactors. The present state of research concerning the flooding behaviour of aerated fluids and suspensions is presented. The author's own investigations, undertaken partly on a semi-technical scale (tank diameter D = 1.5 m) show the most important parameters of this undesirable aerated state during the operation of stirred reactors. For a given stirrer speed the superficial gas velocity, the tank size, and the fluid viscosity are important. Solid particles sediment out when flooding is reached.An objective measuringmethod for determining the occurrence of flooding was adopted.

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Population Dynamics and Environmental Variability

Cited by 11 publications

References 14 publications

Temporal Variations in Annual Production and Biomass in Estuarine Populations of two Polychaetes, Nephtys Hombergi and Ampharete Acutifrons

Temporal Variations in Annual Production and Biomass in Estuarine Populations of two Polychaetes, Nephtys Hombergi and Ampharete Acutifrons

Monitoring the marine environment of Long Island Sound at Millstone Nuclear Power Station, Waterford, Connecticut : summary of studies prior to Unit 3 operation / [prepared by the Environmental Laboratory staff of Northeast Utilities Service Company].

Zum überflutungsverhalten zwei‐ und dreiphasig betriebener Rührreaktoren

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