Energy budgest, growth and filtration rates in Mytilus edulis at different algal concentrations

112

The suspension-feeding activity of Cei-astoderrna edule (L ) was investigated in response to a wide range of experimental seston concentrations which approximated the changes in seston quality and quantity found in the natural environment over tidal cycles of sediment resuspension. The different seston concentrations were produced by adding increasing quantities of resuspended fine sediment to a relatively low and constant algal concentration (0.59 mg dry wt I-'). The total seston concentrations (total particulate matter) varied over a wide range from 1.6 to 570 mg l", and the organic fraction (particulate organic matter) between 0.62 and 79.8 mg 1-' The organic content of the diets decreased with the increasing seston concentration, from 38.8% at the lowest concentration to 14 % at the highest concentration. A significant negative relationship was found between clearance rate of C. edule and seston concentration, with very low values at 570 mg 1-' of total seston. Filtration rate increased with seston concentration from a minimum value of 2.67 mg h-' at the lowest concentration to a maximum of 84.0 mg h-' at a concentration of 300 mg I-'. Above 300 mg 1-' there was an abrupt decline in filtration rate. Pseudofaeces production started at a concentration of 4.8 mg 1 ', showing its highest values at around 300 mg I-' The organic content of pseudofaeces was significantly lower than the organic content of the seston, suggesting that C. edule is able to preferentially select organic particles for ingestion instead of inorganic particles. Selection efficiency was maintained at a high and constant level at seston concentrations between 4.8 and 97 mg 1-', declining at the highest seston concentrations with the lowest organic content. Thus the physiological sorting and selection mechanism appears to be very effective at seston concentrations below 100 mg 1-l, this ability declining abruptly at higher concentrations. Ingestion rate was constant in the lower range of seston concentration (1.6 to 34 mg 1-l), increased at concentrations around 250 mg I-', and declined abruptly at the higher food rations. Absorption efficiency appeared relatively independent of seston concentrations over a large range, but it was reduced at concentrations above 250 mg 1-' We found a very effective digestive mechanism to regulate absorption rate at seston concentrations between 1.6 and 250 mg I-' The results suggest that C. edule can compensate efficiently for a decrease in seston quality over a wide range of seston concentration (1.6 to 300 mg I-') by maintaining an effective preingestive mechanism of selection for organic particulate matter, as well as increasing filtration and rejection rates. As a consequence, this species is well adapted to living in turbid environments, such as intertidal mudflats, which are characterised by marked fluctuations in seston quality and quantity, caused by resuspension of fine sedirnents during periods of high current velocities on the flood or ebb tides.

Section: Discussionmentioning

confidence: 99%

Feeding physiology of Cerastoderma edule in response to a wide range of seston concentrations

Jm¹,

Widdows²

1997

112

“…Several laboratory studies have been carried out during the last decade on bivalve molluscs with the aim of determining the energy budget of Mytilus edulis (Thompson and Bayne, 1974;RiisgArd and Randlev, 1981; for larvae see Sprung, 1984a, b, c, d), Mytilus chilensis (Navarro and Winter, 1982), Aulacomya ater (Griffiths and King,l9?9), Choromytilus meridionalis (Griffiths, 1980), Ostrea edulis (Buxton et al, 1981), Crassostrea virginica (Langefoss and Maurer, 1975), and Crassostrea gigas (Gerdes, 1983a, b).…”

Section: Discussionmentioning

confidence: 99%

Quempillen estuary, an experimental oyster cultivation station in southern Chile. Energy balance in Ostrea chilensis 1

Winter¹,

Acevedo²,

Navarro³

1984

Rates of filtration, ingestion, assimilation, biodeposition, excretion and respiration of the Chilean flat oyster Ostrea chilensis Philippi were determined in laboratory experiments in order to establish energy budgets in relation to body size and 2 different food concentrations of the unicellular green alga Dunaliella marina. Ingestion and assimilation rates are kept constant within the range of food concentrations tested due to corresponding reductions in filtration activity with increasing food densities. The most favourable energy budget (P = aWb) was obtained at the lowest food concentration tested (0.54 mg algal dry wt 1-l; 12OC, 20 %O S) with an a-value of 25.48, when relating the energy disposable for growth and reproduction (Pi cal d l ) to body size (W; dry-tissue wt, g). At the highest food concentration tested (1.07 mg 1 1 ) , the corresponding a-value of 17.38 was significantly lower. The relatively low scope for growth in 0. chilensis is explained by a low species-specific filter-feeding activity and by the high energetic costs of routine metabolism which in a 1 g oyster (dry-tissue wt) vary between 58 and 62 % of the energy ingested. The net growth efficiencies (K,) decreased with increasing body size (from 50 mg to 3000 mg dry-tissue wt) from 53.7 to 22.6 % at the lowest food level and from 51.1 to 13.9 % at the highest food level tested. Comparison of estimated growth (calculated on the basis of the most favourable energy budget), with growth actually measured in oysters from natural banks and tray cultures, shows that the energy budgets established in the present study indeed reflect the conditions experienced by the oysters in their natural environment.

“…At steady-state, the filtration rate (= Cl of 100% efficiently retained algal cells) was calculated as F s (ml h -1 ind. (Riisgård & Randløv 1981), where DR = dosing rate of algal culture (ml time ), and n = number of filter-feeding amphipods.…”

Section: Methodsmentioning

confidence: 99%

Filter feeding in the burrowing amphipod Corophium volutator

Møller¹,

Riisgård²

2006

The present study shows that when suspended phytoplankton cells are present at sufficiently high concentrations the tube-dwelling marine amphipod Corophium volutator (Pallas) filter feeds, but when the phytoplankton biomass reaches a certain low level, both laboratory and field video observations support the hypothesis that C. volutator can switch to surface deposit feeding. Feeding behaviour and quantification of water processing were studied in individuals transferred to glass tubes. Simultaneous clearance of algal cells of different size showed that the setae filter on the second gnathopods retains particles ≥7 µm. The pumping rate (P, ml h -1 ) was measured by video particle tracking, and the relationship between P and body dry weight (W, mg) was found to be P = 53.3W 0.76 . The relationship between P and body length (L, mm) was P = 0.24L 3 + 7.8, and the relationship between temperature (T, °C) and P was P = 5.55T + 3.3. The respiration rate of a 6.5 mm length individual was 0.7 µl O 2 h -1 (15°C), and by relating respiration to P of an individual of this size, it was estimated that C. volutator pumps 108 l water ml -1 O 2 consumed, thus fulfilling the conditions for classification as a true filter feeder. Monthly samples were collected for 1 yr from the shallow (0.8 m) inner part of Odense Fjord (Denmark) in order to follow size and density distribution of C. volutator. By combining filtration rate data with size-and temperature-dependent P data, the area-specific population filtration rate varied between 0.9 in January and 19.4 m 3 m -2 d -1 in June. The half-life of phytoplankton (assuming 100% particle retention efficiency and efficient vertical mixing of the water column) ranged from 14.5 h in January to 0.7 h in June and July. This suggests that the grazing impact of C. volutator may be significantly important in the inner Odense Fjord and other shallow water areas with dense populations of C. volutator.