Epibiotic Communities of Common Crab Species in the Coastal Barents Sea: Biodiversity and Infestation Patterns

Crabs are important ecosystem engineers in marine habitats worldwide. Based on long-term data, we analyzed the species composition and infestation indices of epibionts and symbionts colonizing the great spider crab, Hyas araneus, and two lithodid crabs—the northern stone crab, Lithodes maja, and the red king crab, Paralithodes camtschaticus—in the coastal zone of the Barents Sea. The epibiotic communities found on great spider crabs were closer to northern stone crabs (33%) compared to red king crabs (25%). The prevalence of mobile symbionts (amphipods, Ischyrocerus, and polychaetes, Harmothoe) and common epibionts, such as barnacles and hydrozoans, was low on great spider crabs and high on the body and in the gills of lithodid crabs. Epiphytes were abundant on great spider crabs but not present on both species of lithodid crabs. Egg symbionts found on H. araneus and P. camtschaticus do not affect their local populations. Differences in the fouling communities found on the three crab species are associated with host size range, surface properties of their carapaces, and behavior patterns.

Elevating Dissolved Oxygen—Reflections on Developing and Using Long-Term Data

This prospectus took me about as long to generate as my 36-year record of working on the issue of northern Gulf of Mexico (nGOM) oxygen deficiency, or so I felt. There was so much to cover, but I focused on the issue of hypoxia on the Louisiana continental shelf from the early 1980s to present and my participation in the research and outreach. Not that I was ignoring other aspects of my academic research career (e.g., stone crab populations and their differences in physiology and larval development along the nGOM coast; settlement of crab megalopae, especially blue crabs, on artificial substrates and their timing with tidal events; oil and gas pollutant discharges in coastal waters of Louisiana, and as Director of the Coastal Waters Research Consortium (CWC) of the Gulf of Mexico Research Initiative (GoMRI), and marsh infaunal researcher. I must say, however, that the journey through the documentation of low dissolved oxygen on the Louisiana continental shelf, and its linkage to the changes in the Mississippi River nutrient loads to the coastal waters of the nGOM, marked a dominant part of my career. This prospectus follows my research and outreach career from my first journey offshore in an outboard to set stations for the transect off Terrebonne Bay in early summer of 1985 to now.

Destabilizing effects on a classic tri-trophic oyster-reef cascade

How interactions among multiple predators affect the stability of trophic cascades is a topic of special ecological interest. To examine factors affecting the stability of the classic tri-trophic oyster reef cascade within a different context, configurations of three predators, including the Gulf toadfish, Gulf stone crab, and oystershell mud crab, were manipulated together with either oyster shell or limestone gravel substrate within a multiple predator effects (MPE) experiment. Additionally, a complimentary set of trait-mediated-indirect interaction (TMII) experiments examined the inhibition of oyster consumption relative to mud-crab size and top predator identity in the absence of other cues and factors. The classic tri-trophic cascade formed by the toadfish-mud crab-oyster configuration was potentially weakened by several interactions within the MPE experiment. Consumption of oysters and mud crabs by the intraguild stone crab was undeterred by the presence of toadfish. Although mud crab feeding was inhibited in the presence of both toadfish and stone crabs, estimated non-consumptive effects (NCEs) were weaker for stone crabs in the MPE experiment. Consequently, the total effect was destabilizing when all three predator species were together. Inhibition of mud crab feeding was inversely related to direct predation on mud crabs within the MPE experiment. Complimentary TMII experiments revealed greater inhibition of mud crab feeding in response to stone crabs under sparse conditions. TMII experiments also implied that inhibition of mud crab feeding could have largely accounted for NCEs relative to oysters within the MPE experiment, as opposed to interference by other mud crabs or top predators. An inverse relationship between mud crab size and NCE strength in the TMII experiment disclosed another potentially destabilizing influence on the tri-trophic-cascade. Finally, although habitat complexity generally dampened the consumption of oysters across MPE treatments, complex habitat promoted mud crab feeding in the presence of toadfish alone. This study underscores how ecological interactions can mediate trophic cascades and provides some additional insights into the trophic dynamics of oyster reefs for further testing under natural conditions.

KARAKTERISASI CHITOSAN DAN CHITOSAN POLYMER MEDIUM DARI CANGKANG KEPITING BATU

Kepiting batu (Grapsus albolineatus) merupakan spesies yang banyak ditemukan di pantai berbatu dan eksoskeletonnya adalah salah sumber potensial chitin-chitosan. Chitosan adalah polimer bersifat polikationik dengan chitosan polymer medium (CPM) yang memiliki molekul lebih sederhana sebagai salah satu turunannya. Tujuan penelitian ini adalah untuk menentukan mutu chitosan dan chitosan polymer medium dari cangkang kepiting batu. Metode yang digunakan pada penelitian ini adalah metode eksperimental. Hasil analisis membuktikan bahwa cangkang kepiting memiliki komposisi 4.17±0.08 air, 54.4±2.78 abu, 6.28±0.05 lemak, 23.48±0.01 protein, 11.70±2.93 kaborhidrat. Karakterisasi chitosan memperlihatkan rendemen sebesar 10±0.70%, kadar air 8.10±0.14%, abu 19.39±0.55%, lemak 6.26±0.37%, protein 8.24±0.34%, karbodidrat 50.03±0.04%, derajat putih 60.61±0.86% , viscositas 7.30±0.42 cps dan derajat deasetilasi 55.92±1.30%. Untuk chitosan polymer medium, rendemennya mencapai 98.33±0.40% dan derajat deasetilasinya sebesar 60.22±0.24%. Chitosan dan chitosan polymer medium dari cangkang kepiting batu (Grapsus albolineatus) masih memenuhi standar yang ditetapkan SNI. Stone crab (Grapsus albolineatus) is a species commonly found in rocky beaches. Its exoskeleton is a good source of chitin and/or chitosan. Chitosan represents a polycationic polymer with chitosan polymer medium (CPM) having simpler molecular formula than chitosan as chitosan’s derivative. The objective of this research was to determine the quality of chitosan and chitosan polymer medium from rock crab’s shells. Experimental method was used in this study with characterization of the crab’s shells showing a composition of 4.17±0.08%, water, 54.4±2.78% ash, 6.28±0.05% fat, 23.48±0.01% protein and 11.70±2.93% carbohydrate. Similar characterization on chitosan revealed a composition of 10±0.70% rendemen, 8.10±0.14% water, 19.39±0.55% ash, 6.26±0.37% fat, 8.24±0.34% protein, 50.03±0.04% charabohydrate, 60.61±0.86% white degree, 7.30±0.42 cps viscosity and 55.92±1.30% degrees of deacetylation. Although chitosan contained similar composition of white degree (60%) and deactylation (60%0 to chitoxan polymer medium, CPM had higher composition of rendemen (98.33±0.40%) than chitosan (10±0.70%). In conclusion, this study shows that chitosan and chitosan polymer medium of G. albolineatus met our national standard (SNI).

Ocean acidification changes the vertical movement of stone crab larvae

Anthropogenic activities are increasing ocean temperature and decreasing ocean pH. Some coastal habitats are experiencing increases in organic runoff, which when coupled with a loss of vegetated coastline can accelerate reductions in seawater pH. Marine larvae that hatch in coastal habitats may not have the ability to respond to elevated temperature and changes in seawater pH. This study examined the response of Florida stone crab ( Menippe mercenaria ) larvae to elevated temperature (30°C control and 32°C treatment) and CO 2 -induced reductions in pH (8.05 pH control and 7.80 pH treatment). We determined whether those singular and simultaneous stressors affect larval vertical movement at two developmental stages. Geotactic responses varied between larval stages. The direction and rate of the vertical displacement of larvae were dependent on pH rather than temperature. Stage III larvae swam upwards under ambient pH conditions, but swam downwards at a faster rate under reduced pH. There was no observable change in the directional movement of Stage V larvae. The reversal in orientation by Stage III larvae may limit larval transport in habitats that experience reduced pH and could pose challenges for the northward dispersal of stone crabs as coastal temperatures warm.

Growth in the northern stone crab Lithodes maja Linnaeus, 1758 (Decapoda: Anomura: Lithodidae), a potential fishery target, in the laboratory

Data are presented on growth in early juvenile (N = 36; 2.05–3.95 mm carapace length) Lithodes maja Linnaeus, 1758 reared at 6 °C in the laboratory, and on growth in males (N = 24; 45.9–113.3 mm carapace length) and females (N = 9; 61.0–81.3 mm carapace length) maintained at 6 °C in the laboratory. Growth rate did not differ significantly among early juvenile, males, or females, and therefore appeared linear across the size range examined. Intermoult period increased with increasing size. Growth and intermoult period models were combined to estimate size at age. Age at maturity appears greater in L. maja than in other species of Lithodes, suggesting that L. maja may be more vulnerable to fisheries overexploitation.