Interplay between filter-feeding zoobenthos and hydrodynamics in the shallow Odense Fjord (Denmark) – Earlier and recent studies, perspectives and modelling

Riisgård, Hans Ulrik; Lassen, Johan; Kortegaard, M.; Møller, Lene Friis; Friedrichs, Michael; Jensen, Mikael Hjorth; Larsen, Poul Scheel

doi:10.1016/j.ecss.2007.04.032

Cited by 30 publications

(13 citation statements)

References 26 publications

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“…In a recent field study, a strong interplay was found between filter feeders and hydrodynamics in the inner part of the shallow Odense Fjord (Riisgård et al 2006 fully mixed flow resulted in a potential half-life for phytoplankton of only 1.3 h, whereas for incompletely mixed water the half-life was 2.7 times longer. A certain grazing impact was evident from vertical chl a profiles, often with strongly reduced near-bottom concentrations, but the impact was not sufficient to identify even the main biophysical processes that prevent suspension feeders from completely controlling the phytoplankton biomass in the inner Odense Fjord.…”

Section: Discussionmentioning

confidence: 99%

Filter feeding in the burrowing amphipod Corophium volutator

Møller¹,

Riisgård²

2006

Mar. Ecol. Prog. Ser.

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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.

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Section: Discussionmentioning

confidence: 99%

Filter feeding in the burrowing amphipod Corophium volutator

Møller¹,

Riisgård²

2006

Mar. Ecol. Prog. Ser.

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“…Changes in seston concentration (i.e., seston removal) over short time periods caused by active suspension feeders in shallow, well-mixed water is essentially determined by feeding rate relative to water volume (Koseff et al 1993;Haamer and Rodhe 2000;Riisgård et al 2007). Equation 5 adds water flow to the relationship, thus providing a simple model that predicts the percent of the water column potentially cleared by an oyster reef in shallow, well-mixed tidal flows under optimum environmental conditions (e.g., temperature, dissolved oxygen concentration).…”

Section: Calculationsmentioning

confidence: 99%

“…It is mainly offered as a tool for estimating the potential short-term impact of a population of suspension-feeding bivalves in shallow, wellmixed waters. As noted above, it includes the minimum number of variables for relating seston depletion to bivalve feeding (Haamer and Rodhe 2000;Riisgård et al 2007). Thus, if the model's major assumptions are met-a wellmixed water column and minimal horizontal transport of seston into or out of the modeled area-it should accurately predict seston removal.…”

Section: Future Studies and The Value Of Our Approachmentioning

confidence: 99%

Seston Removal by Natural and Constructed Intertidal Eastern Oyster (Crassostrea virginica) Reefs: A Comparison with Previous Laboratory Studies, and the Value of in situ Methods

Grizzle

Greene

Coen

2008

Estuaries and Coasts

106

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An important ecological role ascribed to oysters is the transfer of materials from the water column to the benthos as they feed on suspended particles (seston). This ecosystem service has been often touted as a major reason for many oyster restoration efforts, but empirical characterization and quantification of seston removal rates in the field have been lacking. Changes in chlorophyll a (chl a) concentrations in the water column were measured in May 2005 and June 2006 in South Carolina using in situ fluorometry and laboratory analysis of pumped water samples taken upstream and downstream as water flowed over natural and constructed intertidal oyster reefs. Both methods gave similar results overall, but with wide variability within individual reef datasets. In situ fluorometer data logged at 10 to 30-s intervals for up to 1.3 h over eight different reefs (three natural and five constructed) showed total removal (or uptake) expressed as % removal of chl a ranging from −9.8% to 27.9%, with a mean of 12.9%. Our data indicate that restored shellfish reefs should provide water-quality improvements soon after construction, and the overall impact is probably determined by the size and density of the resident filter feeder populations relative to water flow characteristics over the reef. The measured population-level chl a removal was converted to mean individual clearance rates to allow comparison with previous laboratory studies. Although direct comparisons could not be made due to the small size of oysters on the study reefs (mean shell height, 36.1 mm), our calculated rates (mean, 1.21 L h −1 ) were similar to published laboratory measured rates for oysters of this size. However, the wide variability in measured removal by the oyster reefs suggests that individual oyster feeding rates in nature may be much more variable than in the laboratory. The proliferation of ecosystem-level models that simulate the impacts of bivalves on water quality based only on laboratory-feeding measurements underscores the importance of further research aimed at determining ecologically realistic feeding rates for oysters in the field. Because in situ methods provide many replicate measurements quickly, they represent a potentially powerful tool for quantifying the effects of oyster reefs, including all suspension-feeding taxa present, on water quality.

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“…However, the additional 'biomixing' induced by the filter feeders themselves (Larsen & Riisgård 1997) has not yet been included in any model. Similar considerations may also be important for dense populations of mussels in nature (Riisgård et al 2004(Riisgård et al , 2007 and in aquaculture systems (Newell et al 1998, Angel et al 2002, Plew et al 2009, Duarte et al 2010. Further progress in understanding and optimizing such systems relies on computational modelling and supporting experiments.…”

Section: Introductionmentioning

confidence: 99%

The exhalant jet of mussels Mytilus edulis

Riisgård¹,

Jørgensen²,

Lundgreen³

et al. 2011

Mar. Ecol. Prog. Ser.

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The exhalant jet flow of mussels in conjunction with currents and/or other mussels may strongly influence the mussels' grazing impact. Literature values of mussel exhalant jet velocity vary considerably and the detailed fluid mechanics of the near-mussel flow generated by the exhalant jet has hitherto been uncertain. Computational modelling of this phenomenon depends on knowledge of the velocity distribution near the exhalant siphon aperture of mussels to provide appropriate boundary conditions for numerical flow models. To be useful such information should be available for a range of mussel shell lengths. Here, we present results of a detailed study of fully open mussels Mytilus edulis in terms of filtration rate, exhalant siphon aperture area, jet velocity, gill area and body dry weight, all as a function of shell length (mean ± SD) over the range 16.0 ± 0.4 to 82.6 ± 2.9 mm, with the corresponding scaling laws also presented. The exhalant jet velocity was determined by 3 methods: (1) measured clearance rate divided by exhalant aperture area, (2) manual particle tracking velocimetry (PTV) using video-microscope recordings, and (3) particle image velocimetry (PIV). The latter provides detailed 2-component velocity distributions near the exhalant siphon in 5 planes parallel to the axis of the jet and the major axis of the oval aperture, and hence estimates of momentum and kinetic energy flows in addition to mean velocity. Data obtained on particles inside the exhalant jet of filtered water was verified by the use of titanium dioxide seeding particles which were de-agglomerated by ultrasound to a size range of 0.7 to 2 µm prior to addition, to avoid retention by the gill filter of the mussels. We found that exhalant jet velocity was essentially constant at ~8 cm s −1 , and independent of shell length. Based on geometric similarity and scaling of mussel pump-system characteristics we found that these characteristics coincide approximately for all sizes when expressed as pressure head versus volume flow divided by shell length squared. KEY WORDS: Filtration rate · Exhalant siphon area · Particle image velocimetry · Particle tracking velocimetry · Exhalant jet velocity · Velocity field · Allometric equation · Scaling law Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 437: [147][148][149][150][151][152][153][154][155][156][157][158][159][160][161][162][163][164] 2011 will influence the grazing impact and thus the concentration distribution of food particles reaching the inhalant aperture; hence affecting the feeding conditions of the mussel. Of particular interest is the undesirable phenomenon of re-filtration where part of the once filtered and exhaled water reaches the inhalant aperture of either the same or other mussels. This has been studied to some extent for mussel beds where a number of attempts have been made to model phytoplankton concentration gradients caused by dense beds of filter-feeding bivalves in relatively strong currents with a high ...

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Interplay between filter-feeding zoobenthos and hydrodynamics in the shallow Odense Fjord (Denmark) – Earlier and recent studies, perspectives and modelling

Cited by 30 publications

References 26 publications

Filter feeding in the burrowing amphipod Corophium volutator

Filter feeding in the burrowing amphipod Corophium volutator

Seston Removal by Natural and Constructed Intertidal Eastern Oyster (Crassostrea virginica) Reefs: A Comparison with Previous Laboratory Studies, and the Value of in situ Methods

The exhalant jet of mussels Mytilus edulis

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