Biodiversity and Biogeography of Chthamalid Barnacles from the North-Eastern Pacific (Crustacea Cirripedia)

The biogeography and ecology of the species of Chthamalus present on the west coast of America are described, using data from 51 localities from Alaska to Panama, together with their zonation on the shore with respect to that of other barnacles. The species present were C. dalli, Pilsbry 1916, C. fissus, Darwin, 1854, C. anisopoma Pilsbry 1916 and four species in the C. panamensis complex. The latter are C. panamensis Pilsbry, 1916, C. hedgecocki, Pitombo & Burton, 2007, C. alani nom. nov. (formerly C. southwardorum Pitombo & Burton, 2007) and C. newmani sp. nov.). These four species were initially separated by enzyme electrophoresis. They could only be partially separated by DNA bar coding but may be separated using morphological characters.

Notes and memoranda

Hermit crabs and anemones Grayling and Loch Leven trout in salt water Eels and sticklebacks in sea water Phoronis at Plymouth Oyster culture in the River Yealm Notes on Ray's bream

The effect of pollution of intertidal sediments on the viability of calanoid copepod eggs

Calanoid copepod eggs have been extracted from intertidal sediments and hatched in the laboratory. Although most of the eggs which hatched did so within < 7 days, the hatching of some continued over a more prolonged period (> 20 days). This indicates that there were a significant number of diapausing or delayed hatching eggs. The species of calanoids present include some of which are known to produce diapausing eggs. Hatching of nauplii from incubated sediment samples was slower than from the extracted eggs indicating dormancy induced by the effects of burial in the sediment. Viability of the eggs has been related to chronic industrial or urban pollution as indicated by polycyclic aromatic hydrocarbon levels. These hatchings were conducted simultaneously with those for cleaner locations. The viability of eggs was significantly depressed in the more heavily polluted sites. An oil spill arising from the grounding of the "Sea Empress" at Milford Haven, UK, in February 1996 has provided a comparison of the impact of an acute situation with these chronic effects. An immediate drastic reduction in viability was followed by a recovery in the year following the spill. The data have provided no evidence for differences in the response to pollution between diapausing and subitaneous eggs.

Reduced pH sea water disrupts chemo-responsive behaviour in an intertidal crustacean

Chemoreception is a key activity by which many aquatic animals perceive their environment, and therefore abiotic disruptions to this process could have serious impacts on the survival and fitness of individuals, and on species interactions. Hermit crabs are subject to cyclical reductions in the pH of the water in the intertidal rock pools that they inhabit. Such reductions may be further exacerbated by ongoing ocean acidification and/or leakage of carbon dioxide from geological storage sites and coastal upwelling events. Here we test the chemo-sensory responses of the hermit crab Pagurus bernhardus (Linnaeus) to a food odour under reduced pH conditions (pHNBS = 6.80). Acidifying the odour had no effect on its attractiveness indicating no permanent degradation of the cue; however, the pH of the sea water did affect the crabs' responses. Hermit crabs kept and tested in reduced pH sea water had lower antennular flicking rates (the ‘sniffing’ response in decapods); were less successful in locating the odour source, and showed an overall decline in locomotory activity compared to those in untreated sea water. Analysis of their haemolymph revealed a greater concentration of chloride ions ([Cl−]) in the reduced pH treatment group, suggesting iono-regulatory disruption; however, there was no correlation between [Cl−] and locomotory activity, suggesting a specific effect on chemoreception. This study shows that the chemo-responsiveness of a crustacean may be influenced by both naturally occurring pH fluctuations and future anthropogenically-induced changes in ocean pH.

Ranking of length-class seasonal and regional effects on dietary compositions of the co-occurring Pagrus auratus (Sparidae) and Pseudocaranx georgianus (Carangidae)

Using an effective combination of multivariate testing and ordination analyses, this study compares the extents to which the diets of two co-occurring fish species (Pagrus auratus and Pseudocaranx georgianus) are related to body size (length class), season and region and the rank order importance of those effects. Thus, volumetric dietary compositions were determined for these species on the lower west coast of Australia, where both are abundant, and for P. auratus from the mid west coast and P. georgianus from the south coast. The diet of P. auratus on the lower west coast was strongly related to body size and slightly less to season. With increasing body size, its diet shifted from predominantly ophiuroids to larger prey, such as brachyuran crabs, teleosts, echinoids and ultimately asteroids, probably reflecting a shift from foraging over soft sediments to areas over and around reefs. Seasonal changes on the lower west coast were restricted mainly to small P. auratus, while larger fish underwent seasonal changes further north. Analyses using a common size range of medium to larger P. auratus demonstrated that dietary composition differed more between regions than seasons. The relationships between diet and length class of P. georgianus on both the lower west and south coasts were less pronounced than for P. auratus and seasonal changes were restricted to the south coast, where amphipod consumption increased markedly in summer. The diet of P. georgianus was related far more to region than length class and season, with more small teleosts, small crabs, carideans and littorinids and less amphipods, isopods and small bivalves being ingested on the lower west than south coasts. Although crabs and teleosts were important typifying prey of P. auratus and P. georgianus, when co-occurring, the former predator tended to ingest greater volumes of larger and often less mobile prey. This reflects differences in dentition, jaw morphology and feeding behaviour and reduces the potential for competition for food resources. The results imply that P. auratus and P. georgianus are opportunistic feeders and that the effects of length class, season and region on dietary composition and their rank orders can vary markedly between species and for length class and season between regions for the same species.

Strong preference for decapod prey by the western rock lobster Panulirus cygnus

Western rock lobsters, Panulirus cygnus are an abundant benthic consumer distributed along the temperate west coast of Australia and constitute the largest single species fishery in Australia. As a dominant consumer, it is important to understand their predator-prey interactions as they can potentially exert strong trophic effects, and may influence ecosystem function as seen in other spiny lobster species. While previous field studies have focused on the diet composition of P. cygnus, this study investigated their preference for various benthic invertebrate prey to better understand the likely predator-prey interactions of P. cygnus. Prey preferences of small sub-legal juvenile lobsters, as well as medium and large legal-sized mature lobsters were investigated using laboratory feeding trials to identify size-associated differences in lobster prey preference. Handling time and diet quality were investigated to estimate energetic cost and gain from consuming different prey which may explain prey choice by lobsters. It was found that large lobsters preferred crabs and mussels while medium and small lobsters preferred crabs over mussels, gastropods, and sea urchins. This suggests that strong predator-prey interactions between P. cygnus and crabs may occur in the wild.

Living in warmer, more acidic oceans retards physiological recovery from tidal emersion in the velvet swimming crab, Necora puber

The distribution patterns of many species in the intertidal zone are partly determined by their ability to survive and recover from tidal emersion. During emersion, most crustaceans experience gill collapse, impairing gas exchange. Such collapse generates a state of hypoxemia and a hypercapnia-induced respiratory acidosis, leading to hyperlactaemia and metabolic acidosis. However, how such physiological responses to emersion are modified by prior exposure to elevated CO2 and temperature combinations, indicative of future climate change scenarios, is not known. We therefore investigated key physiological responses of velvet swimming crabs, Necora puber, kept for 14 days at one of four pCO(2)/temperature treatments (400 mu atm/10 degrees C, 1000 mu atm/10 degrees C, 400 mu atm/15 degrees C or 1000 mu atm/15 degrees C) to experimental emersion and recovery. Pre-exposure to elevated pCO(2) and temperature increased pre-emersion bicarbonate ion concentrations [HCO3-], increasing resistance to short periods of emersion (90 min). However, there was still a significant acidosis following 180 min emersion in all treatments. The recovery of extracellular acid-base via the removal of extracellular pCO(2) and lactate after emersion was significantly retarded by exposure to both elevated temperature and pCO(2). If elevated environmental pCO(2) and temperature lead to slower recovery after emersion, then some predominantly subtidal species that also inhabit the low to mid shore, such as N. puber, may have a reduced physiological capacity to retain their presence in the low intertidal zone, ultimately affecting their bathymetric range of distribution, as well as the structure and diversity of intertidal assemblages.

Benthic megafauna and CO2 bubble dynamics observed by underwater photography during a controlled sub-seabed release of CO2

In 2012, a controlled sub-seabed release of carbon dioxide (CO2) was conducted in Ardmucknish Bay, a shallow (12 m) coastal bay on the west coast of Scotland. During the experiment, CO2 gas was released 12 m below the seabed for 37 days, causing significant disruption to sediment and water carbonate chemistry as the gas passed up through the sediment and into the overlying water. One of the aims of the study was to investigate how the impacts caused by leakage from geological CO2 Capture and Storage (CCS) could be detected and quantified in the context of natural heterogeneity and dynamics. To do this underwater photography was used to analyze (i) the benthic megafaunal response to the CO2 release and (ii) the dynamics of the CO2 bubble streams, emerging from the seabed into the overlying water column. The frequently observed megafauna species in the study area were Virgularia mirabilis (Cnidaria), Turritella communis (Mollusca), Asterias rubens (Echinodermata), Pagurus bernhardus (Crustacea), Liocarcinus depurator (Crustacea), and Gadus morhua (Osteichthyes). No discernable abnormal behavior was observed for these megafauna, in any of the zones investigated, during or after the CO2 release. Time-lapse photography revealed that the intensity and presence of the CO2 bubble plume was affected by the tides, with the most active bubbling seen at low tides and the larger hydrostatic pressure at high tide suppressing CO2 bubbling from the seabed.

Investigation of benthic community change over a century-wide scale in the western English Channel

Since the early part of the 20th Century the impact of a range of anthropogenic activities in our coastal seas has steadily increased. The effect of such activities is a major cause for concern but in the benthic environment few studies exist that date back more than a few decades. Hence understanding long term changes is a challenge. Within this study we utilized a historic benthic dataset and resurveyed an area west of Eddystone reef in the English Channel previously investigated 112 years ago. The aim of the present work was to describe the current benthic community structure and investigate potential differences between 1895 and 2007. For each of the four major phyla investigated (Polychaeta, Crustacea, Mollusca and Echinodermata), multivariate community analysis showed significant differences between the historic and contemporary surveys. Echinoderm diversity showed a clear reduction between 1895 and 2007. The sea urchins Echinus esculentus, Spatangus purpureus, and Psammechinus miliaris and large star-fish Marthasterias glacialis showed reductions in abundance, in some cases being entirely absent from the survey area in 2007. Polychaetes showed a shift from tubiculous species to small errant and predatory species such as Glycera, Nephtys, and Lumbrineris spp. Within the group Mollusca large species such as Pecten maximus and Laevicardium crassum decreased in abundance while small species increased. Crustaceans in 1895 were dominated by crab species which were present in similar abundances in 2007, but, the order Amphipoda appeared to show a significant increase. While some of the differences observed could stem from differences in methodologies between the surveys, in particular increases of small cryptic species, the loss of large conspicuous species was judged to be genuine. The study area is an important beam trawling and scallop dredging ground; the differences observed are concomitant with changes generally associated with disturbance from demersal fishing activities such as these.