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Coastal seas are critical components of the global carbon cycle, yet little research has been conducted on the impact of ocean acidification on coastal benthic organisms. Calcifying marine organisms are predicted to be most vulnerable to a decline in oceanic pH (ocean acidification) based on the assumption that calcification will decrease as a result of changes in seawater carbonate chemistry, particularly reduced carbonate ion concentration (and associated saturation states). Net calcium carbonate production is dependent on an organism's ability to increase calcification sufficiently to counteract an increase in dissolution. Here, a critical appraisal of calcification in five benthic species showed, contrary to popular predictions, the deposition of calcium carbonate can be maintained or even increased in acidified seawater. This study measured changes in the concentration of calcium ions seen in shells taken from living animals exposed to acidified seawater. These data were compared with data f...

The Arctic Ocean and its associated ecosystems face numerous challenges over the coming century. Increasing atmospheric CO2 is causing increasing warming and ice melting as well as a concomitant change in ocean chemistry (“ocean acidification”). As temperature increases it is expected that many temperate species will expand their geographic distribution northwards to follow this thermal shift; however with the addition of ocean acidification this transition may not be so straightforward. Here we investigate the potential impacts of ocean acidification and climate change on populations of an intertidal species, in this case the barnacle Semibalanus balanoides, at the northern edge of its range. Growth and development of metamorphosing post-larvae were negatively impacted at lower pH (pH 7.7) compared to the control (pH 8.1) but were not affected by elevated temperature (+4 °C). The mineral composition of the shells did not alter under any of the treatments. The combination of reduced growth and maintained mineral content suggests that there may have been a change in the energetic balance of the exposed animals. In undersaturated conditions more mineral is expected to dissolve from the shell and hence more energy would be required to maintain the mineral integrity. Any energy that would normally be invested into growth could be reallocated and hence organisms growing in lowered pH grow slower and end up smaller than individuals grown in higher pH conditions. The idea of reallocation of resources under different conditions of pH requires further investigation. However, there could be long-term implications on the fitness of these barnacles, which in turn may prevent them from successfully colonising new areas.

Ocean acidification and global warming are occurring concomitantly, yet few studies have investigated how organisms will respond to increases in both temperature and CO2. Intertidal microcosms were used to examine growth, shell mineralogy and survival of two intertidal barnacle post-larvae, Semibalanus balanoides and Elminius modestus, at two temperatures (14 and 19°C) and two CO2 concentrations (380 and 1,000 ppm), fed with a mixed diatom-flagellate diet at 15,000 cells ml−1 with flow rate of 10 ml−1 min−1. Control growth rates, using operculum diameter, were 14 ± 8 μm day−1 and 6 ± 2 μm day−1 for S. balanoides and E. modestus, respectively. Subtle, but significant decreases in E. modestus growth rate were observed in high CO2 but there were no impacts on shell calcium content and survival by either elevated temperature or CO2. S. balanoides exhibited no clear alterations in growth rate but did show a large reduction in shell calcium content and survival under elevated temperature and CO2. These results suggest that a decrease by 0.4 pH(NBS) units alone would not be sufficient to directly impact the survival of barnacles during the first month post-settlement. However, in conjunction with a 4–5°C increase in temperature, it appears that significant changes to the biology of these organisms will ensue.

The effects of CO2-induced acidification on survival, shell mineralogy, embryonic devel- opment and the timing of larval release were investigated in the intertidal barnacle Semibalanus bal- anoides using an intertidal microcosm system. Compared to that in the control (CO2 = 344 ppm, pH = 8.07), adult survival was 22% lower in the high-CO2 treatment (CO2 = 922 ppm, pH = 7.70) and sig- nificant changes in the mineral structure of the adult shell were observed. Embryonic development rate was significantly slower in the high-CO2 treatment than in the control but still resembled 'nat- ural' rates seen in populations found in similar locations. There was an estimated 19 d delay in devel- opment under high-CO2 conditions, which resulted in a 60% reduction in the number of nauplii reaching hatching stage at the time when over 50% of the control nauplii had hatched. We conclude that ocean acidification could potentially further compromise embryonic development in a species already stressed by temperature, which could in turn impact naupliar development and recruitment. S. balanoides, the adults of which live in a highly variable environment, has been shown to be detri- mentally impacted by a chronic change in chemical conditions (pH lowered beyond the current range) over a crucial period in their life cycle. Under experimental high-CO2 conditions, some adults were able to survive and larvae were able to hatch. This may indicate that there is still potential for organisms to find suitable habitats and for populations to develop and survive.

Macroecology provides a novel conceptual framework for analysis of the distribution and abundance of organisms at very large scales. Its rapid development in recent years has been driven primarily by studies of terrestrial taxa; the vast potential of marine systems to contribute to the macroecological research effort remains largely untapped. International collaborative efforts such as MarBEF have provided fresh impetus to the collation of regional databases of species occurrences, such as the newly available MacroBen database of the European soft sediment benthic fauna. Here, we provide a first macroecological summary of this unique database. We show that in common with almost all previously analysed assemblages, the frequency distribution of regional site occupancies across species in the MacroBen database is strongly right-skewed. More unusually, this right skew remains under logarithmic transformation. There is little evidence for any major differences between higher taxa in this frequency distribution (based on the 8 animal classes for which we have sufficient data). Indeed, considerable variation in occupancy persisted across the taxonomic hierarchy, such that most variation occurred between species within genera. There was a weak positive relationship between local population density and regional occupancy across species, but this abundance–occupancy relationship varied considerably between higher taxa and between geographical areas. Our results highlight the potential of databases such as MacroBen to consolidate macroecological generalities and to test emerging theory.

The pan-European MacroBen database was used to compare the AZTI Marine Biotic Index (AMBI) and the Benthic Quality Index (BQIES), 2 biotic indices which rely on 2 distinct assessments of species sensitivity/tolerance (i.e. AMBI EG and BQI E[S]0.05) and which up to now have only been compared on restricted data sets. A total of 12 409 stations were selected from the database. This subset (indicator database) was later divided into 4 marine and 1 estuarine subareas. We computed E(S50)0.0 in 643 taxa, which accounted for 91.8% of the total abundances in the whole marine indicator database. AMBI EG and E(S50)0.05 correlated poorly. Marked heterogeneities in E(S50)0.0 between the marine and estuarine North Sea and between the 4 marine subareas suggest that sensitivity/tolerance levels vary among geographical areas. High values of AMBI were always associated with low values of BQIES, which underlines the coherence of these 2 indices in identifying stations with a bad ecological status (ES). Conversely, low values of AMBI were sometimes associated with low values of BQIES resulting in the attribution of a good ES by AMBI and a bad ES by BQIES. This was caused by the dominance of species classified as sensitive by AMBI and tolerant by BQIES. Some of these species are known to be sensitive to natural disturbance, which highlights the tendency of BQIES to automatically classify dominant species as tolerant. Both indices thus present weaknesses in their way of assessing sensitivity/tolerance levels (i.e. existence of a single sensitivity/tolerance list for AMBI and the tight relationship between dominance and tolerance for BQIES). Futurestudies should focus on the (1) clarification of the sensitivity/tolerance levels of the species identifiedas problematic, and (2) assessment of the relationships between AMBI EG and E(S50)0.05 within and between combinations of geographical areas and habitats.

In recent years the non-native polychaete Sternaspis scutata has rapidly expanded its range in inshore muddy sediments along the coast of SW England (UK). To determine the impact the arrival of this moderately large infaunal deposit feeding polychaete could have on benthic biodiversity and ecosystem function, a mesocosm experiment has been conducted. Sternapsis scutata were added to undisturbed sediment cores containing natural fauna. Individuals of S. scutata were added at densities 2x and 10x the current abundance of this species at the collection site in Plymouth Sound. Nutrient fluxes and macrobenthic diversity were assessed after a period of fifty days. Despite the very large increase in biomass caused by the addition of S. scutata to the sediment cores there was no significant difference in the diversity of the resident benthic biota in treated cores. It is concluded that despite its size, the relative immobility of S. scutata dictates that its presence has little impact on the species around it. The addition of this species did significantly reduce the release of nitrite (NO2-) and increase the release of ammonium (NH4+) from the sediment. These findings support the assertion that the relationship between biodiversity and ecosystem functioning is idiosyncratic.

In addition to the predicted rise in temperature, a recognised consequence of increased atmospheric CO2 is ocean acidification. The response of marine organisms to the stresses associated with acidification is still not understood, and a number of recent experiments have addressed this problem. The starting point for many of these studies has been the development of a system by which seawater pH can be altered and then maintained. The current paper presents details of a tempera- ture- and pH-controlled microcosm system, which enables the establishment of a tidal regime, for the experimental investigation of intertidal organisms. Two climate scenarios were simulated to evaluate the system's precision and accuracy; Year 2008 ('low' (CO2): 380 ppm and 14°C) conditions and Year 2100 ('high' (CO2)) conditions (based on the IPCC—Intergovernmental Panel on Climate Change— 2007 A2 scenario, 'high' (CO2): 1250 ppm and 2.0 to 5.4°C warming). The temperature and seawater carbonate chemistry were reliably maintained for 30 d during which time newly settled barnacle cyprids were allowed to metamorphose into juveniles, then grow and develop. The pH and (CO2) had 95% confidence intervals of ±0.03 units and ±17 ppm, respectively, under low (CO2) conditions, and of ±0.02 units and ±43 ppm, respectively, under high (CO2) conditions. The tidal regime is fully adjust- able, and on this occasion was set to a 6 h cycle. These microcosms have proved ideal for studying ben- thic organisms from a variety of near-surface environments and at different stages of their life-cycle.

Since the rate of global climate change began to accelerate in the 1980s, the coastal seas of Britain have warmed by up to 1°C. Locations close to the northern range edges of a southern trochid gastropod Osilinus lineatus in Britain previously surveyed in the 1950s and 1980s were resurveyed during 2002–2004 to determine whether changes in the success of near-limit populations had occurred during the period of climate warming. Between the 1980s and the 2000s, the range limits had extended by up to 55 km. Populations sampled over a latitudinal extent of 4 degrees from northern limits towards the centre of the range showed synchronous increases in abundance throughout the years sampled, suggesting a large-scale factor such as climate was driving the observed changes. These increases in abundance and changes in range limits are likely to have occurred via increased recruitment success in recent years.

The diversity of soft-bottom polychaete assemblages in one Antarctic (Admiralty Bay) and two Arctic (Kongsfjord and van Mijenfjord) localities was compared. The data sets included 79 (Admiralty Bay), 80 (Kongsfjord) and 44 (van Mijenfjord) samples collected with use of 0.1 m2 van Veen grab. The number of species per sample in Kongsfjord (mean 19.9 ± 8.0 SD) was higher than that in Van Mijenfjord (13.7 ± 8.3) or Admiralty Bay (15.7 ± 9.4). The differences in species numbers reflected differences in numbers of individuals in samples: 310.4 ind/0.1 m2 ± 178.0 in Kongsfjord, 132.7 ind/0.1 m2 ± 88.7 in Van Mijenfjord and 138.9 ind/0.1 m2 ± 91.5 in Admiralty Bay. The Hurlbert diversity for 50 individuals (ES[50]) was similar at all sites: 10.7 ± 3.4 in Kongsfjord, 9.7 ± 4.2 in van Mijenfjord, 10.5 ± 4.9 in Admiralty Bay. The shape of species accumulation curves was also similar for all localities. There was no significant difference (at P < 0.05) either in the total number of species or in species richness as estimated by Chao1 and Chao2 estimators. The generic and family richness at three sites was also similar. We found no substantial differences in the distribution of species among families. At both poles Terebellidae, Ampharetidae, Maldanidae, Spionidae and Polynoidae were dominant in terms of species numbers. The similarity of infaunal polychaete diversity at the polar sites studied contrasts with the substantial differences reported for epi-megafauna. Our study suggests that the patterns of diversity of polar benthic communities are shaped by patterns of habitat heterogeneity which appears to mask any historical processes.

The activity of Arctic tidal glaciers results in high turbidity, high rate of inorganic particulate sedimentation and sedimentary instability in near-glacier marine basins. The chronic physical disturbance of sediments is accompanied by low input levels of organic matter. The response of soft-bottom macrofauna to glacial disturbance was studied in Kongsfjord, Svalbard. The quantita- tive characteristics of the macrofauna of 4 associations located along a gradient of glacier-induced disturbance were examined. Benthic biomass decreased with increased proximity to the glacier (from 10.9 g wet weight (ww) m -2 in the outermost association to 2.7 g ww m -2 in the glacial bay). Faunal density was highest in the transitional zone (592 ind. 0.1 m -2 ) between the central basin (425 ind. 0.1 m -2 ) and the inner glacial bay (442 ind. 0.1 m -2 ). The average individual biomass was lowest in the glacial bay as a result of the smaller body size of organisms. A decrease in the size of organisms in disturbed sites was not accompanied by a classical shift from 'equilibrium' to 'opportunistic' species. The functional structure of the faunal associations was simplified in the impoverished glacial bay association where 1 guild, the mobile surface-detritus feeders, strongly dominated. Average species number per sample was lowest in the glacial bay (22 species) and highest in the transitional associa- tion (42 species). Species diversity expressed by the Shannon-Wiener and Hurlbert rarefaction indices and evenness expressed by the Pielou index was lower in the glacial bay than in the remain- ing associations. The decrease in biomass, mean size of organisms, species diversity and evenness as well as the peaked distribution (i.e. maximum in the transitional zone) of density and species richness are consistent with patterns reported in studies of different natural and anthropogenic disturbances. Some distinct features of the case of glacial-induced disturbance include relatively high taxonomic distinctness and low beta diversity and low faunal dispersion in the near-glacier association.

High-latitude seas are mostly covered by multi-year ice, which impacts processes of primary production and sedimentation of organic matter. Because of the warming effect of West Spitsbergen Current (WSC), the waters off West Spitsbergen have only winter ice cover. That is uncommon for such a high latitude and enables to separate effects of multiyear-ice cover from the latitudinal patterns. Macrofauna was sampled off Kongsfjord (791N) along the depth gradient from 300 to 3000 m. The density, biomass and diversity at shallow sites situated in a canyon were very variable. Biomass was negatively correlated with depth (R ¼� 0:86; po0.001), and ranged from 61 g ww m � 2 (212 m) to 1 g ww m � 2 (2025 m). The biomasses were much higher than in the multiyear-ice covered High Arctic at similar depths, while resembling those from temperate and tropical localities. Species richness (expressed by number of species per sample and species–area accumulation curves) decreased with depth. There was no clear depth-related pattern in diversity measures: Hurbert rarefaction, Shannon–Wiener or Pielou. The classic increase of species richness and diversity with depth was not observed. Species richness and diversity of deep-sea macrofauna were much lower in our study than in comparable studies of temperate North Atlantic localities. That is related to geographic isolation of Greenland–Icelandic–Norwegian (GIN) seas from the Atlantic pool of species. r 2004 Elsevier Ltd. All rights reserved.

The relative impact on macrofaunal diversity of 7 naturally co-occurring bioturbators has been examined in a benthic mesocosm experiment. The bioturbators chosen were selected because of their potential vulnerability to the disturbances associated with demersal trawling. The experiment was conducted at the Solbergstrand mesocosm (Norwegian Institute for Water Research) using subtidal sediment collected from Bjornehodebukta, a small sheltered bay in the Oslofjord. For 3 of the bioturbating species (Brissopsis lyrifera, Aphrodita aculeata and Amphiura chiajei) a positive, linear relationship was demonstrated between bioturbator abundance and measures of species rich- ness (number of species and Margalef species richness). It was suggested that the presence of these bioturbating species increased oxygen penetration into the sediment, leading to an enhancement in the ability of benthic systems to process organic material. This had a beneficial effect on the associ- ated fauna in terms of maintaining levels of diversity. For Nephtys caeca, highest species diversity was seen in the low abundance treatments. Predation by N. caeca on small polychaetes is proposed as a possible explanation of the lower diversity in high-density treatments. It is concluded that B. lyrifera, A. aculeata, A. chiajei and N. caeca are functionally similar with respect to setting the diversity of the associated macrobenthic community and may therefore fulfill the same role within the benthic ecosystem. The presence of Calocaris macandreae, Nuculana minuta and Astarte sulcata had no detectable effect on diversity. Trawling has been shown to reduce the abundance of bioturbating species, and the current study demonstrates important implications of this loss on the maintenance of diversity. In addition, the interactions between bioturbation, diversity and organic enrichment high- light the need for management of anthropogenic impacts within the coastal environment in a holistic way rather than by isolation.

The spatial scale of megafaunal assemblage variation in apparently homogeneous subtidal sediment was investigated using quantitative observations from a remotely operated vehicle (ROV). Quantitative abundance estimates of surface-dwelling megafauna and biotic sediment features associated with burrowing megafauna were derived from video images using the Automated Benthic Image-Scaling System (ABISS), a novel method of applying scale to images collected by ROVs. Spatially referenced images were collected with a maximum sample separation of 400 m within a broader area of apparently homogeneous sediment in Plymouth Sound (Devon, UK) during May 2000 and March 2001. Rank-correlograms were constructed to examine the extent and form of the megafaunal spatial structure. The megafaunal assemblage was neither uniformly distributed nor temporally stable. A hierarchy of spatial structure was detected within the megafaunal assemblage, whereby patches with minimum radius between 123 and 163 m were nested within patches up to 400-m radius. The approach described in this paper offers ways forward to address how variation of megafaunal spatial structure affects macrofaunal assemblage structure and to discuss the application of remote imaging to map and predict the conservation value of subtidal soft sediments.

The standard method for collecting information on both the abundance and distribution of surface-dwelling megafauna, and biotic sediment-features associated with burrowing megafauna has been direct observation and counting by divers. However, remote observations allow information comparable to diver observations to be applied to investigations at greater depths and over wider spatial extents than divers may achieve. The present paper compares abundance estimates of megafaunal biotic sediment-features obtained from diver and remotely operated vehicle-mapping techniques. Results show strong agreement between estimates of total-feature and conspicuous- feature abundance, providing assurance that remote observation techniques are not subject to systematic errors in estimation of feature abundance. The ability to detect the smallest features appeared to differ between observation techniques, but this was an artefact caused by measurement of features rather than feature detection. A laser diode array attached to the camera to quantify image scale increased the amount of quantitative data that may be extracted from remote images.

Species body size spectra have been constructed for macrofauna assemblages from four sites with contrasting sediment granulometry and heterogeneity in and around Plymouth Sound. The number of species and species turnover (β diversity) were higher on coarse sediment. While the fauna were distinct between sites, the median geometric size-class was conservative (class 14; 0.153–0.305 mg dry blotted weight). Only one site had significantly lower heterogeneity within the species size spectrum, yet this was the most heterogeneous sediment. As such, we were unable to reject the null hypothesis that species body size distribution patterns are conservative despite differences in sediment granulometry and heterogeneity.

The spatial scale of local patterns in the fauna of two contrasting shallow water sediment assemblages has been investigated using hierarchical sampling. Replicate samples were taken at separations of 50 cm, 5 m, 50 m and 500 m. No significant differences between samples could be detected on any of these scales in a fine sand assemblage. However, in a heavily bioturbated sandy mud, samples separated by more than 50 m were significantly different from each other. This separation was largely a result of changes in the pattern of dominance among the most abundant species, particularly annelids. In a complimentary set of analyses, animals were regrouped either by higher taxa or by body size. The numerically important annelids and crustaceans showed a pattern of spatial similarity close to the full data set, but that shown by molluscs was clearly distinct. Large bodied animals were also independent of the main pattern while smaller species conformed to it. In the case of the latter, separation of sites at the 50 m scale could be related to patterns of species richness as well as dominance.

Experimental manipulations of food supply were performed on soft sediment cores from two European estuaries, the Westerscheldt and the Gironde, with a view to determining benthic macrofaunal community response. Over a period of twenty weeks in a laboratory mesocosm system, both communities showed losses in terms of numbers of individuals and small, but non-significant, losses in terms of numbers of species. Whereas no effect of the different types of foods or the dose levels at which they were supplied was detected for the Westerscheldt benthic community, that of the Gironde showed some significant response. This was largely attributed to the differential mortality of spionid polychaetes across the dose levels used, with the highest dose, equivalent to 200 g C m−2 yr−1, only just maintaining their initial population densities. The results are discussed in terms of the importance of lateral advection of food particles at the benthic boundary layer and the general insufficiency of many estimates of carbon input to shallow benthic systems.

The pattern of occurrence and recent changes in the distribution of macrobenthic organisms in fjordic and coastal (nearshore) Arctic waters are reviewed and future changes are hypothesized. The biodiversity patterns ob- served are demonstrated to be contextual, depending on the specific region of the Arctic or habitat type. Two major areas of biotic advection are indicated (the North Atlantic Current along Scandinavia to Svalbard and the Bering Strait area) where larvae and adult animals are transported from the species-rich sub-Arctic areas to species-poor Arctic areas. In those Arctic areas, increased temperature associ- ated with increased advection in recent decades brings more boreal-subarctic species, increasing the local biodiversity when local cold-water species may be suppressed. Two other large coastal areas are little influenced by advected waters; the Siberian shores and the coasts of the Canadian Archipelago. There, local Arctic fauna are exposed to increasing ocean temperature, decreasing salinity and a reduction in ice cover with unpredictable effect for biodiversity. One the one hand, benthic species in Arctic fjords are exposed to increased siltation (from glacial meltwater) and salinity decreases, which together may lead to habitat homogenization and a subsequent decrease in biodiversity. On the other hand, the innermost basins of Arctic fjords are able to maintain pockets of very cold, dense, saline water and thus may act as refugia for cold- water species.

As part of a programme to re-assess the existence of latitudinal gradients in the diversity of the macrobenthic infauna of soft sediments, samples were taken from Sassenfjord, Spitzbergen. Abundancebiomass curves showed the shallowest sites to be moderately disturbed, possibly as a result of glacial run-off from the Gipselva. These clearly differed from a site at 123 m which appeared to be in an undisturbed state. A comparison of the diversity profile of the latter site (78 °N) with those of physically similar sites in the North Sea (55 °N) and off the coast of Java (7 °S), sampled by identical methods, shows no real difference in diversity.

Species abundance data for benthic communities, collected during 1971–1988 off Northumberland on the north-east coast of England (western North Sea) and the Skagerrak (eastern North Sea), and pelagic data collected in corresponding areas during 1958–1988 by the Continuous Plankton Recorder (CPR) survey have been subjected tomulti-dimensional scaling ordination. Changes in community structure at the two benthic stations show a high degree of similarity, characterised by a transition in the late 70s. Similarly, there is a less marked transition between the 70s and 80s in pelagic community structure from the eastern North Sea but pelagic data from the western North Sea shows no discernible patterns. Benthic community biomass data, available only for the Skagerrak station, enabled abundance/biomass comparison curves to be constructed which demonstrated a change from un-disturbed communities in the early and mid 70s to moderately disturbed communities in the late 70s and 80s. North Sea macrofaunal abundance, and, in the Skagerrak, macrofaunal biomass appear to co-vary with phytoplankton colour and total zooplankton abundance, although there are insufficient data for statistical testing. A number of factors including eutrophication and/or pollution may be responsible for these changes in community structure.

At a large North Sea pockmark, with active methane seeps, surface sediments were found to have higher insoluble sulphide concentrations than sedlments from the surrounding area. The fauna of the pockmark was characterized by 2 species which have not pi-evlously been reported from the Fladen Ground in the northern North Sea. These species were a b~valve, Thyasira sarsi (which is known to contain endosymbiotic sulphur-oxidising bacteria) and a mouthless and gutless nematode, Astomonerna sp., which also contains endosymbiotic bacteria The nematode was the dominant meiofauna species in the pockmark sediments. Both macro-lnfauna and total nematodes were in low abundance in samples taken from the base of the pockmark. Sediment samples from the pockmark contained numerous otoliths, implying that substantial winnowing of the sediment had taken place. This was supported by studies on the sulphide concentrations in the sediment which showed multiple layering of the sediments on the sides of the pockmark, suggesting displacement. The carbon isotope compositions (6I3c) of the tissues of benthic animals from in and around the pockmark were generally in the range -16 to -2O%, indicating that little methane-derived carbon was contributing to their nutrition. T sarsi had the most 13c-depleted tissues, -31.4 to -35.1 L, confirming the nutritional dependence of this species on chemoautotrophic bacteria that utilize reduced sulphur.

Several recent studies have shown the potential value of chloroform-soluble fluorescent age pigments (FAPs) in determining the age of marine invertebrates with no permanent hard parts. The primary assumption in estimating age from FAPs is that there is a linear (or at least monotonie) increase in FAP content with time. We have tested this assumption with the trochid gastropod Monodonta lineata , a species whose age can be established unequivocally from shell growth checks. Samples of 10 age classes (1.5–10.5 yr) were obtained and FAPs extracted from lyophilised cerebral ganglia and digestive gland. The fluorescence emission spectra were similar to those reported for other organisms, though the wavelength of maximum intensity varied with tissue, sex and age. Cerebral ganglia often showed two major emission peaks, digestive gland only one. Thin-layer chromatography indicated that at least three fluorescent compounds were present in the extracts. Digestive gland total FAP content did not vary for the first 5 yr of growth, but then trebled during the next 5 yr. The tissue concentration of FAP showed no statistically significant trend. Cerebral ganglia total FAP content increased during the first 5 yr then remained constant for the next 3 yr before declining. There was a steady decline in the concentration of cerebral ganglion FAP throughout life. These patterns indicate a complex relationship between FAP content and calendar age, and indicate that (at least in Monodonta ) FAPs have little practical value for determining age.

Seasonal changes in the rate of shell formation frequently affect the surface morphology of molluscan shells, with reductions in feeding activity and calcification rates at low temperatures producing winter rings that can be used for age determination. Such annuli are well-known in lamellibranchs and have greatly facilitated studies on their growth, longevity and other age-related processes (as reviewed by Wibur & Owen, 1964; Rhoads & Panella, 1970; Comfort, 1957, 1979). However, they occur less frequently in gastropods and many species that do show such checks are relatively short-lived, or else their growth ceases or becomes erratic on sexual maturity.

The recruitment of the trochid gastropods Gibbula umbilicalis and Monodonta lineata was studied between 1978 and 1984 at Aberaeron in mid-Wales. In the former species the post winter density of ‘O’ class animals varied greatly (