Comparison of shallow-water seston among biogenic habitats on tidal flats

Aquatic structure-formers have the potential to establish mosaics of seston in shallow water if they modify the relative amounts of deposition (or filtration) and resuspension of particles. By sampling surface water adjacent to Lagrangian drifters traveling 0.1 to 2 m above the bottom, we tested the modification of seston in water masses flowing over two biogenic marine species (native eelgrass, Zostera marina; introduced oysters, Crassostrea gigas) in comparison to unstructured tidal flats. Water properties were examined at five intertidal sites in Washington State, USA, each with 27 drifts (three drifts at different stages of the tidal cycle in each of three patches of three habitat types; drift distance 116 m (109SD), duration 24 min (15SD)). At the initiation of each drift, habitat differences in water properties were already apparent: chlorophyll-a and total suspended solid (TSS) concentrations were greater in structured habitats than bare, and TSS was also inversely related to water depth. Water flowed more slowly across eelgrass than other habitat types. As water flowed across each habitat type, TSS generally increased, especially in shallow water, but without habitat differences; chlorophyll-a in these surface-water samples showed no consistent change during drifts. At higher TSS concentrations, quality in terms of organic content declined, and this relationship was not habitat-specific. However, quality in terms of chlorophyll-a concentration increased with TSS, as well as being greater in water over eelgrass than over other habitat types. These results support widespread mobilization of seston in shallow water ebbing or flooding across Washington State’s tidal flats, especially as water passes into patches of biogenic species

Sediment characteristics and interspecific interaction influence the distribution of Emerita talpoida and Donax variabilis in swash

The mole crab Emerita talpoida and the coquina clam Donax variabilis inhabit the swash zone of the American Atlantic coast, riding waves to follow the advance and retreat of the tide. Uneven distribution of these animals along Cape Henlopen, DE, led to a hypothesis that any factor that slows burrowing will prove limiting to crab or clam settlement in the limited window of low flow that accompanies the high point of a wave. In the laboratory, crabs and clams burrowed in sediments of varied coarseness and sortedness, and crabs also burrowed in the presence and absence of clams. Small crabs burrowed significantly more slowly in coarser sands, while sortedness did not affect crab burrowing. Clams burrowed significantly more slowly in coarse/sorted sand. Crabs burrowed significantly more slowly in the presence of clams. In the field, there was no significant correlation between sediment characteristics and crab number, while there was a significant negative correlation between sortedness and clam number. Numbers of crabs and clams exhibited no significant correlation. Differences between these species in absolute burrowing speeds may suggest that factors that slow burrowing prove limiting to slow-burrowing clams, but not to rapid-burrowing crabs

Variation in Survival and Gut Microbiome Composition of Hatchery-Grown Native Oysters at Various Locations within the Puget Sound.

The Olympia oyster (Ostrea lurida) of the Puget Sound suffered a dramatic population crash, but restoration efforts hope to revive this native species. One overlooked variable in the process of assessing ecosystem health is association of bacteria with marine organisms and the environments they occupy. Oyster microbiomes are known to differ significantly between species, tissue type, and the habitat in which they are found. The goals of this study were to determine the impact of field site and habitat on the oyster microbiome and to identify core oyster-associated bacteria in the Puget Sound. Olympia oysters from one parental family were deployed at four sites in the Puget Sound both inside and outside of eelgrass (Zostera marina) beds. Using 16S rRNA gene amplicon sequencing of the oyster gut, shell, and surrounding seawater and sediment, we demonstrate that gut-associated bacteria are distinct from the surrounding environment and vary by field site. Furthermore, regional differences in the gut microbiota are associated with the survival rates of oysters at each site after 2 months of field exposure. However, habitat type had no influence on microbiome diversity. Further work is needed to identify the specific bacterial dynamics that are associated with oyster physiology and survival rates. IMPORTANCE This is the first exploration of the microbial colonizers of the Olympia oyster, a native oyster species to the West Coast, which is a focus of restoration efforts. The patterns of differential microbial colonization by location reveal microscale characteristics of potential restoration sites which are not typically considered. These microbial dynamics can provide a more holistic perspective on the factors that may influence oyster performance

Using Real-Time Polymerase Chain Reaction to Determine Spatial Distribution of Multiple Species of Shellfish

The success of both wild and cultured shellfish populations is dependent upon recruitment of planktonic larvae. Due to issues of cost, time, expertise and inaccuracy associated with bivalve identification using microscopy, real-time polymerase chain reaction is being employed to identify and quantify larvae using DNA technology. We are quantifying species-specific abundance and distribution of four commercially important species using novel approaches. Environmental samples were collected via two rounds of in-situ pumping at four locations in intertidal waters in Washington State. Pumping was performed at two depths: near the water surface and above the sea floor and at two times: before sunrise and sunset, in order to determine the spatial and temporal distribution of bivalve larvae. Genetic assays for Pacific geoduck clam (Panopea generosa) Olympia oyster (Ostrea lurida), Pacific oyster (Crassostrea gigas) and Manila clam (Venerupis philippinarum) have been designed. The collected field samples are currently undergoing qPCR quantification using these assays. Results will be analyzed to determine cross-species patterns or species-specific behavior in larval distribution throughout Washington State. This information will provide a comprehensive snapshot of the larvae of multiple shellfish species in Washington. Additionally, this information may further be utilized by hatcheries by providing the best times and locations for hatcheries to plant cultured seeds and substrate and by researchers studying the effects of localized ocean acidification

The winner goes to: A comparison of techniques to identify and quantify bivalve larvae in environmental samples in Washington State

Reliable detection and quantification of bivalve larvae during critical life stages is crucial in forecasting population abundance, recruitment, behavior, and dispersal. Therefore, it is scientifically and commercially valuable to develop an efficient method to quantify larval presence and abundance. Commonly used methods for approximating larval abundance involve distinguishing morphological differences between bivalve species in environmental plankton samples (EPS) by microscopy. This method is problematic during earlier stages of larval development and rely on high amounts of expertise in bivalve larvae identification. Most recently, approaches using TaqMan probe-based multiplex real-time polymerase chain reaction (RT-PCR) to quantify copies of DNA in comparison to a standard curve of known larvae has been successfully applied to cultivated larval samples. However, few studies have performed comprehensive comparisons of these methods using EPS. In the present study, assays to determine absolute quantification using a standard curve of the Pacific geoduck clam (Panopea generosa), Pacific oyster Crassostrea gigas), Olympia oyster (Ostrea lurida), and Manila clam (Venerupus phillipinarum) were developed and compared to microscopy techniques using morphological traits of the same species in two pulses of EPS at four relevant sites throughout Washington State. Preliminary results indicate the resourcefulness of using TaqMan chemistry to detect larval presence in known amounts of cultured larvae spiked in mock-up plankton samples as well as the presence of bivalve larvae in collected EPS. We predict that high-throughput RT-PCR will prove to be less time consuming and more reliable than microscopy in quantifying species specific abundances in EPS