Hydrodynamic enhancement of invertebrate larval settlement in microdepositional environments: colonization tray experiments in a muddy habitat (original) (raw)
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Settlement of Macoma balthica larvae in response to benthic diatom films
Marine Biology, 2009
The role of multi-species benthic diatom Wlms (BDF) in the settlement of late pediveliger larvae of the bivalve Macoma balthica was investigated in still-water bioassays and multiple choice Xume experiments. Axenic diatom cultures that were isolated from a tidal mudXat inhabited by M. balthica were selected to develop BDF sediment treatments characterized by a diVerent community structure, biomass, and amount of extracellular polymeric substances (EPS). Control sediments had no added diatoms. Although all larvae settled and initiated burrowing within the Wrst minute after their addition in still water, regardless of treatment, only 48-52% had completely penetrated the high diatom biomass treatments after 5 min, while on average 80 and 69% of the larvae had settled and burrowed into the control sediments and BDF with a low diatom biomass (<3.5 g Chl a g ¡1 dry sediment), respectively. The percentage of larvae settling and burrowing into the sediment was negatively correlated with the concentration of Chl a and EPS of the BDF. This suggests higher physical resistance to bivalve penetration by the BDF with higher diatom biomass and more associated sugar and protein compounds. The larval settlement rate in annular Xume experiments at Xow velocities of 5 and 15 cm s ¡1 was distinctly lower compared to the still-water assays. Only 4.6-5.8% of the larvae were recovered from BDF and control sediments after 3 h. Nonetheless, a clear settlement preference was observed for BDF in the Xume experiments; i.e., larvae settled signiWcantly more in BDF compared to control sediments irrespective of Xow speed. Comparison with the settlement of polystyrene mimics and freeze-killed larvae led to the conclusion that active selection, active secondary dispersal and, at low Xow velocities (5 cm s ¡1), passive adhesion to the sediment are important mechanisms determining the settlement of M. balthica larvae in estuarine bioWlms. Communicated by J. P. Grassle.
Settlement of benthic marine invertebrates
Marine Ecology Progress Series, 1993
Settlement and recruitment of benthic marine invertebrates are complex processes, determined by the interaction of biotic and abiotic factors which operate at different temporal and spatial scales. This review analyses the settlement process, attempting to integrate aspects related to different levels of organization (i.e. ecological-physiological-molecular). This is important because many factors that act at any of these levels and at different times can explain by themselves the patterns of settlement andlor recruitment of a large number of species. From an ecological perspective, progress has been made in the identification of causal factors of vanations in larval availability for settlement. Many physical and ethological factors that act during settlement have, however, not received much attention. Likewise, since the great majority of settlement studies have been carried out at restricted spatial scales, fewer works consider different biological and physical factors acting at different scales simultaneously. Settlement patterns are frequently inferred from recruitment. In this sense, a density-independent action of post-settlement mortality has been cons~dered as prerequisite for thls type of inference. This has, however, recently been challenged on the basis that settler-recruit and mortality-settler density relationships change in time. At the physiological-molecular level, different settlement-inducing chemical cues have been identified. Those cues have, however, not yet been characterized to understand better the signal transduction mechanisms involved in larval responses. It is likely that the nervous system is involved. The use of artificial inducers would be useful in studying settlement induction, until more effective natural inducers are isolated and characterized Although few studies have analysed the acquisition of competence, stages of larval development have been related to changes in protein patterns or enzymatic levels of the nervous system. An inopportune exposure of larvae to inducers may delay settlement and may even have a negative impact on growth and subsequent survival of juveniles.
Journal of Experimental Marine Biology and Ecology, 1993
To test whether larval settlement patterns of the opportunistic bivalve Mulinia lateralis (Say) and the opportunistic polychaete Capitella sp. I are influenced by near-bottom flow, laboratory still-water and flume-flow experiments were conducted using a sediment-filled array consisting of depressions and compartments flush with the flume bottom. Compartments were filled with organic-rich mud or a low-organic, glass-bead mixture of a comparable grain size. Previous flume experiments have shown that larvae of both species settle in greater numbers in mud compared with glass beads. Depressions create a hydrodynamic environment that traps passive particles, permitting tests of the relative importance of active selection versus passive deposition of larvae in regions of microtopography.
Further insights into the responses of macroinvertebrate species to burial by sediment
Hydrobiologia
The impact of fine sediments on both habitat quality and macroinvertebrate communities of riverine systems has been well documented over recent years. However, there is a paucity of studies examining the mechanisms that relate macroinvertebrate sensitivity and responses of individual macroinvertebrate species to burial by sediment. Laboratorybased burial experiments were undertaken to study the response of some EPT species including Baetis rhodani, Ecdyonurus insignis, Rhithrogena semicolorata, Hydropsyche siltalai, Rhyacophila dorsalis and the amphipod Gammarus duebeni to burial. A range of burial conditions were studied which included five sediment fractions at two burial depths. Responses were variable across species and, overall, the ranking of the determinants that impacted on species responses to burial was burial depth [ sediment class [ species source, with no detectable effect linked to body size. Increased burial depth had the most marked effects on emergence times, while slower escape times were also observed from the finer sediment classes. Species source also influenced responses with some upland species taking longer or failing to emerge from burial. Further mechanistic studies, based on EPT species, are required to enhance our understanding of how and at what level sediment affect species, an essential step in developing pressure-specific biological metrics.
Effects of deposited sediment on invertebrate drift: An experimental study
New Zealand Journal of Marine and Freshwater Research, 2001
The effect of deposited sediment on invertebrate drift was experimentally assessed by adding fine sediment to three of six cobble-lined artificial channels. One invertebrate species, Deleatidium spp., was added to the channel after the addition of sediment, whereas other taxa had colonised the channel naturally before the addition of sediment. Invertebrate drift was collected from each channel after the added sediment had worked its way into the interstitial spaces of the cobbles. Drift was collected every evening and morning for 3 days, after which time benthic densities in the channels were assessed. The percentage of benthos in the drift was significantly higher from sediment-treated channels than from untreated channels for Paracalliope fluviatilis, Oxyethira albiceps, Hydrobiosis sp., and chironomid larvae. Drift of these animals from sediment-treated channels was more than double that from untreated channels, with an average of over 5% of the benthos drifting from the sediment-treated channels per day. Although there was no difference in the percentage of Deleatidium in the benthos that drifted from treated or untreated channels, significantly more individuals drifted from treated channels. Deposition of fine sediment had no significant effect on chironomid emergence or diurnal drift patterns for the taxa in the experiment. Periphyton communities in sediment-treated channels were characterised by reduced chlorophyll a and increased inorganic content. We could not determine whether increased drift caused by deposited sediment reflected decreases in suitable habitat, reductions in food quality of the algae, or both.
Viability of invertebrate diapausing eggs collected from residual ballast sediment
Limnology and Oceanography, 2003
Natural or anthropogenic movement of sediments may be an important vector for the dispersal of invertebrate resting stages between water bodies. Here we record the presence of invertebrate diapausing eggs in residual sediments from transoceanic vessels and explore whether these may pose an invasion risk. Viability of diapausing eggs was explored under light and dark conditions using sediment collected from eleven tanks on nine vessels operating on the Great Lakes. Seventeen cladoceran, copepod, and rotifer taxa were identified. Four of the species hatched have not yet been reported as established in the Great Lakes. Egg viability for individual species varied from 0% to 92%. Exposure to saline water may impact egg viability of some freshwater species. Generally, the proportion of eggs hatched in light and dark treatments did not differ significantly, indicating that light was not required to terminate diapause. As a result, eggs could potentially hatch in dark ballast tanks when immersed in freshwater loaded as ballast during operation on the Great Lakes. Viability of diapausing eggs differed among ballast tanks on a single vessel, indicating that tanks with independent ballast histories have different invasion risks. While additional work is needed to quantify risk, results from this study indicate that vessels entering the Great Lakes with only residual ballast are a potential vector for the introduction of new nonindigenous species during multiport operations. Freshwater invertebrates achieve dispersal via transport of their desiccation-resistant dormant stages in flowing waters, wind, or by ectozoochorous or endozoochorous animal vectors (see Bilton et al. 2001; Cáceres and Soluk 2002; Figuerola and Green 2002). Water currents are likely responsible for most short-distance dispersal events, particularly of stream-dwelling taxa (Bilton et al. 2001). Wind and animal vectors also disperse invertebrates (Figuerola and Green
Journal of Marine Research, 1992
Experiments on larval settlement of the opportunistic polychaete, Capitella sp. I, using three natural sediment treatments from the Buzzards Bay area (organic-rich mud from Sippewissett Marsh, organic-rich mud from New Bedford Harbor and low-organic sand from off the Weepecket Islands), and a glass bead mixture similar in grain size distribution to the New Bedford Harbor mud, were carried out in still water and two flume flows (near-surface velocities of 5 cm S-I and 15 cm S-I; boundary-shear velocities of 0.26 cm S-I and 0.64 cm S-I). For all three flow conditions the larvae settled in significantly greater numbers in the two mud treatments than in the glass beads. In some experiments there was significant discrimination between one or both mud treatments and sand. There was significantly higher settlement in sand than in glass beads in two of three experiments in both slow and fast flow. There was no difference in the ability of larvae to discriminate between the sediment treatments in the slow and fast flow. Strong row and column effects in the settlement of larvae in flow experiments (row 1 at the leading edge and column 4 toward the inner wall of the flume having the highest settlement)
Marine Ecology Progress Series, 1996
We predicted that both refuge dimension and growth form would influence settlement and short-term post-setUement success (57 d) of sessile marine invertebrates that live attached to hard substrata in low energy environments. Individuals with unlimited attachment to the substrata should rapidly be protected by their growth form, thus decreasing their need to settle in refuges and limiting the length of time any locations on heterogeneous substrata act as refuges. Alternatively, organisms with limited attachment to the substrata should remain susceptible to the causes of mortality for a longer time, and as a result should settle in high quality refuges [sites that protect individuals from competitors, predators or physical disturbance events until either a size refuge or reproductive maturity is obtained). Results agreed with these predictions for 4 species of invertebrates examined on both the topographically complex surface of the solitary ascidian Styela plicata (hereafter Styela) and on settlement plates w~t h uniformly spaced roughness elements that mimicked the heights of roughness elements (2.0 and 5.0 rnm) found on Styela in Beaufort, North Carollna, USA. On all surfaces, the 2 species with limited attachment to the substrata, Balanus sp. (aclonal, solitary) and Bugula neritina (clonal, arborescent), settled almost exclusively in the location that provided individuals with the best refuge: the crevices formed where the bases of roughness elements intersect with the flat surfaces. Additionally, when roughness elements of various heights were present (Styela, range: 0 6 to 8.8 mm), intermediate size roughness elements (2.0 < X 1 5. 0 mm) were picked over 72% of the time. Settlement locations and locations where survival were enhanced were less consistent for the 2 species with unlimited attachment to the substrata: a clonal, encrusting form (Schjzoporella errata) and a clonal stolon-mat form (Tubularia crocea). Fewer individuals of these 2 species settled on roughness elements on Styela and when they did, they were not restricted to the bases of the roughness elements. On the plate surfaces, most settlement did occur in crevices, but both species grew away from this location w~thin days and short-term survival was not consistently greater in this location. Additional trials were run on plates with pits of the same maximum dimensions as the tested roughness elements (2.0 and 5.0 mm depth) to see i f crevices and pits provide refuges of equal quality for newly settled individuals. Only survival of Balanus sp. recruits was greatest in both crevlces and pits. Evidence for active choice of settlement location comes from consistent results in trials in which some larvae settled in greater numbers on specific size roughness elements on Styela and in areas of high erosion. Overall, these results show that one must be very cautious when generalizing about refuge quality on heterogeneous surfaces, and to determine if a location is a spatial refuge, it is critical to consider: (1) the dimensions of the larva, (2) the relative dimensions of the individual and potential refuge location at any point in time from the moment settlement occurred, and (3) the growth form of the individual which is related to its need for protection from biotic and abiotic sources of mortality.