Habitat value of a developing estuarine brackish marsh for fish and macrocrustaceans

Abstract Marsh creation receives worldwide attention in mitigating loss of coastal wetlands and in management retreat of estuaries. In the Westerschelde, the former Selena Polder, south from the marsh of Saeftinghe, developed into the Sieperda marsh after several dyke breaches. Soon after the tides regained access to the polder, a tidal creek was formed. After 10 years, a developing marsh system was found adjacent to a mature marsh system. This situation offered the opportunity to compare the utilization by nekton species of a natural mature marsh with a recently created developing marsh under similar circumstances. Between April and October 1999, both the mature Saeftinghe marsh and the developing Sieperda marsh were sampled every 6 weeks on 2 consecutive days. Each sampling occasion covered the whole tidal cycle. The most important environmental parameters (water height, temperature, salinity, turbidity and dissolved oxygen) were similar in both marsh creeks. A distinct difference in nekton community structure between the two marshes was observed. The total biomass and densities of nekton species were higher in Saeftinghe. In Saeftinghe, a density peak occurred in July and was mainly due to large numbers of the mysid, Neomysis integer. In Sieperda, maximum abundance of the mysid, Mesopodopsis slabberi, caused the peak density in September. This difference in species dominance was observed in all samples. Biomass peaked in July in the mature marsh and in October in the developing marsh. Mysid shrimp (N. integer) and fish (mainly Pomatoschistus microps) were the main contributors to the biomass Saeftinghe. Herring, sprat (Clupeidae) and shore crab (Carcinus maenas) were more important in Sieperda. For P. microps, distinct differences in length–frequency distributions were noted between the marshes. While creek morphology influences the abundance and species composition of visiting nekton, the age of a marsh and its maturity are believed to be the prime factors in determining the habitat function of creek systems of developing and mature marshes.

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Circatidal Moulting Rhythm in The Shore Crab Carcinus Maenas

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315400033981 ◽

1997 ◽

Vol 77 (1) ◽

pp. 277-279 ◽

Cited By ~ 10

Author(s):

P. Abello ◽

C.G. Warman ◽

E. Naylor

Keyword(s):

High Tide ◽

Carcinus Maenas ◽

Temporal Patterns ◽

Shore Crab ◽

Male And Female ◽

Large Numbers ◽

Free Running ◽

First Time

Late premoult females from precopula pairs of male and female Carcimts maenas (Crustacea: Brachyura) moulted at times of expected high tide in constant conditions in the laboratory. The data presents for the first time evidence of endogenous, circatidal (−12·4 h) moulting rhythms in a crustacean.Studies on the temporal patterns of moulting in crustaceans have elucidated rhythms of seasonal (annual or biannual), lunar (29·4 d), semilunar (14·7 d) and diel (24 h) periodicities (see Conan, 1985; Fernandez et al., 1994). Examples in the literature of so-called ‘tidal’ rhythmicity of moulting given by Conan (1985) are more correctly referred to as semilunar or neap/spring patterns. There appear to be no reported examples of true tidal (12·4 h) moulting rhythms. Also there is very little evidence in the literature that moulting rhythms phased to geophysical cycles are controlled endogenously. Most studies have been carried out in the field or under L:D cycles in the laboratory and only a few have been undertaken with animals in constant conditions (see Fowler et al., 1971; Bishop & Herrnkind, 1976; Nicol, 1989; Fernandez et al., 1994). Conan (1985) has reported moulting rhythms of circamonthly, circatidal (=circasemilunar) and circadian periodicities but his use of the prefix ‘circa’ is unusual since it more correctly describes free-running rhythms in constant conditions, not environmentally driven rhythms as in the examples quoted. In the present study we sought to determine whether moulting in the shore crab Carcimts maenas (L.) was tidally patterned and endogenous.Over a period of several days in the summer of 1991 large numbers of premoult female Carcinus maenas were obtained by searching for specimens associated with males in precopular pairs.

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THULIUM BIOACCUMULATION BY THE SHORE CRAB CARCINUS MAENAS COLLECTED FROM THE FRENCH COASTS OF THE CHANNEL : A STRUCTURAL, ULTRASTRUCTURAL AND MICROANALYTICAL STUDY BY SECONDARY ION MASS AND X RAY SPECTROMETRY

Le Journal de Physique Colloques ◽

10.1051/jphyscol:19842123 ◽

1984 ◽

Vol 45 (C2) ◽

pp. C2-541-C2-544

Author(s):

C. Chassard-Bouchaud ◽

P. Hallegot ◽

M. Meignan

Keyword(s):

Carcinus Maenas ◽

Shore Crab ◽

X Ray ◽

Secondary Ion

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Heritability of the Effect of Corticosteroids on Intraocular Pressure

Acta geneticae medicae et gemellologiae ◽

10.1017/s1120962300025658 ◽

1970 ◽

Vol 19 (1-2) ◽

pp. 264-267 ◽

Cited By ~ 4

Author(s):

F.H. Reuling ◽

J.T. Schwartz

Keyword(s):

Intraocular Pressure ◽

Clinical Signs ◽

Topical Steroids ◽

Frequency Distributions ◽

Steroid Response ◽

Large Numbers ◽

Wide Range ◽

Allele Pair ◽

High Level ◽

Genetically Determined

In the late 1950's and early 1960's, it became evident that some glaucoma patients developed elevations of intraocular pressure, which were difficult to control, following prolonged use of systemic or ocular medications containing corticosteroids (Chandler, 1955, Alfano, 1963; Armaly, 1963). In addition, some patients without glaucoma, when treated with steroids for long periods of time, developed clinical signs of chronic simple glaucoma (McLean, 1950; François, 1954; Covell, 1958; Linner, 1959; Goldman, 1962). Fortunately, the elevation of intraocular pressure was reversible if the drug was discontinued.Over the past decade, extensive investigation of the “steroid response” has been undertaken. For this presentation, the steroid response may be considered as a gradual elevation of intraocular pressure, occurring over several weeks, in an eye being medicated with corticosteroid drops several times a day. The elevation in pressure is usually accompanied by a reduction in the facility of aqueous outflow. When relatively large numbers of subjects were tested with topical steroids, so that a wide range of responsiveness could be observed, a variation in individual sensitivity was demonstrated. Frequency distributions of intraocular pressure or change in pressure following steroids showed a skew toward the high side. On the basis of trimodal characteristics which they observed in such frequency distributions, Becker and Hahn (1964), Becker (1965) and Armaly (1965, 1966) considered the possible existence of several genetically determined subpopulations. These investigators distinguished three subpopulations on the basis of low, intermediate, and high levels of pressure response. It was hypothesized that these levels of response characterized three phenotypes, corresponding to the three possible genotypes of an allele pair, wherein one member of the pair determined a low level of response, and the other member determined a high level of response (Armaly, 1967).

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