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Journal of Experimental Marine Biology and Ecology 245 2000 69–81
www.elsevier.nl locate jembe
Egestion rates of the estuarine mysid Neomysis integer Peracarida: Mysidacea in relation to a variable environment
a b
a ,
S.D. Roast , J. Widdows , M.B. Jones
a
Plymouth Environmental Research Centre Department of Biological Sciences, University of Plymouth,
Plymouth , Devon PL4 8AA, UK
b
Centre for Coastal and Marine Sciences , Plymouth Marine Laboratory, Prospect Place, West Hoe,
Plymouth , Devon PL1 3DH, UK
Received 21 August 1998; received in revised form 23 March 1999; accepted 7 October 1999
Abstract
The hyperbenthic, estuarine mysid Neomysis integer Crustacea: Mysidacea is exposed to wide fluctuations of temperature and salinity on tidal and seasonal cycles. Using sieved sediment as an
environmentally relevant food source and egestion rates as a measure of ingestion, the feeding rates of N
. integer have been quantified at temperatures 5, 10 and 158C and salinities 1, 10, 20
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and 30‰ experienced in the field. Egestion rates 0.017–0.049 mg faeces mg dry wt. mysid
21
h increased with increasing temperature Q
values ranged from ¯ 1.9–2.4 and with
10
increasing salinity. There was a significant interaction between temperature and salinity such that egestion rates were suppressed at high temperature 108C in combination with high salinity
30‰. Male egestion rates were not significantly different from those of females at any temperature salinity combination. Absorption efficiency ¯ 0.35 was unaffected by temperature
or salinity, confirming that egestion rates are representative of energy acquisition by N
. integer. In the estuarine environment, mysid feeding rates are predicted to be low for much of the tidal cycle
as the sites occupied by N . integer are dominated by low salinity, cold river water.
2000
Elsevier Science B.V. All rights reserved.
Keywords : Estuarine mysids; Sediment; Egestion rates; Feeding; Temperature; Salinity
1. Introduction
Mysids Crustacea: Peracarida contribute significantly to the secondary production of estuaries. The hyperbenthic mysid Neomysis integer dominates the upper regions of
Corresponding author. Tel.: 144-175-223-2911; fax: 144-175-223-2970. E-mail address
: mjonesplymouth.ac.uk M.B. Jones 0022-0981 00 – see front matter
2000 Elsevier Science B.V. All rights reserved.
P I I : S 0 0 2 2 - 0 9 8 1 9 9 0 0 1 5 2 - 5
70 S
.D. Roast et al. J. Exp. Mar. Biol. Ecol. 245 2000 69 –81
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European estuaries and has an estimated productivity of 300 mg ash-free dry weight m
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year in the Westerschelde Estuary Netherlands Mees et al., 1994. As many mysids
are hyperbenthic, they are thought to provide a significant link in the exchange of organic matter between the benthic and pelagic systems of estuaries, however, published
data on the contribution of mysids to such food fluxes are limited Moffat, 1996; Mees and Jones, 1998; Roast et al., 1998a. While it is well established that the feeding rates of
many crustaceans are influenced by various factors including temperature, salinity, weight, gender and food density Kinne, 1970, 1971; Newell and Branch, 1980; Toda et
al., 1987; Guerin and Stickle, 1995, few of these factors have been investigated for mysids. Previous investigations of mysid feeding have concentrated on filter feeding and
predatory feeding Cooper and Goldman, 1982; Fulton, 1982; Webb et al., 1987; Chigbu and Sibley, 1994. In laboratory feeding experiments, mysids are generally fed brine
shrimp Artemia sp. nauplii Astthorsson, 1980; Collins et al., 1991 or Daphnia magna Irvine et al., 1993, food items not representative of their normal diet. Stomach content
analyses have indicated that mysids feed on a wide variety of foods including detritus Mauchline, 1980. For N
. integer, amorphous material from sediment flocs has been identified as an important food item Fockedey and Mees, 1999.
The aims of the present study were to establish the effects of temperature and salinity on the feeding rates of Neomysis integer using an environmentally relevant food source,
and to interpret the implications of these laboratory findings to mysids in the natural environment. To achieve the latter, mysids were collected from the East Looe River
Estuary, Cornwall UK, where details of seasonal and tidal fluctuations of water temperature, salinity and current velocity are available Roast et al., 1998b; 1999.
2. Materials and methods
