Effects of marine reserves on the reproductive biology and recruitment rates of commonly and rarely exploited limpets

We tested the effects of marine reserve status on the reproductive biology and recruitment rates of two commonly exploited (Helcion concolor, Scutellastra longicosta) and two rarely exploited (Cellana capensis, Scutellastra granularis) limpet species using two reserve and two non-reserve sites on the south coast of South Africa. Because densities of commonly exploited species are lower outside reserves, we hypothesised that limpets outside reserves will: (i) mature earlier; and (ii) show higher individual reproductive output. Rarely exploited species should show no such effects. For recruitment, we hypothesised that if recruits are attracted to adults or survive better where there are more adults, then commonly exploited (but not rarely exploited) species should show higher recruitment inside reserves. Analyses of gonadosomatic indices produced significant Month × Reserve interactions for all species (ANCOVA, p < 0.05), indicating inconsistent reserve effects even for exploited species, although months with significant differences occurred more often in the commonly exploited species, giving weak support to the hypothesis regarding reproductive output. Reserve status had no significant effect on sex ratios or size at sexual maturity for either sex of any species. Accordingly, reserves had only a minor influence on reproduction in these species, which might reflect an indirect effect of poor policing. The timing of major recruitment events differed among species, with two broad patterns: recruitment was sporadic for C. capensis and S. longicosta and protracted for H. concolor and S. granularis. Recruit densities showed strong site effects. Highest recruitment occurred at the exploited site, Xhora, with no reserve effects, except in a single month for C. capensis, indicating that recruitment is independent of whether the site is protected or not. Therefore, reserves do not enhance recruitment directly, but because these populations appear to be open on scales of tens of kilometres, generally higher densities of limpets within reserves could enhance overall recruitment, because of greater gamete output by the population. Accordingly, reserves might have an indirect ‘spillover’ effect on recruitment, if not a direct one.     

Marine Protected Areas in the Mediterranean Sea: Objectives, Effectiveness and Monitoring

Abstract. The number of Marine Protected Areas (MPAs) is continuously increasing worldwide because of the increasing recognition of the profound effects that humans can have on marine systems. A large body of literature deals with marine reserves and their potential as conservation and management tools. In several cases, empirical evidence demonstrated that reserves can harbour greater diversity, higher abundance, and larger organisms than unprotected areas. In most cases, however, reserve design and site selection involved little scientific justification, with no direct test of most of the mechanisms assumed to work in a marine reserve. Field investigations of subtidal marine reserves are generally confounded by intrinsic ecological differences between sites investigated inside and outside reserves, by a lack of site and reserve replication, or by the absence of information about the biota before reserve establishment. This is particularly true in the Mediterranean Sea. The aim of this paper is to show that, at least in the Mediterranean basin, the effectiveness of MPAs has been rarely demonstrated because of lack of appropriate sampling designs. An MPA can be considered as a zone subjected to human impact, presumably a positive one. As a consequence, we propose the use of experimental procedures generally utilised for detecting environmental impacts.     

Macroalgal associations of motile epifaunal invertebrate communities on coral reefs

Small grazing motile epifaunal invertebrates play an important ecosystem role on coral reefs, influencing both the abundance and composition of macroalgal communities and acting as a key food source for a range of predatory fishes. The first aim of this study was to investigate the associations between motile epifaunal communities and four common macroalgal species (Lobophora variegata, Dictyota divaricata, Microdictyon marinum and Halimeda opuntia) on fore‐reef environments in the Exuma Cays (Bahamas, wider Caribbean). Secondly, we investigated the implications of the well documented rise of Caribbean macroalgal cover on invertebrate densities by surveying sites inside and outside the Exuma Cays Land and Sea Park (ECLSP), where increases in parrotfish grazing intensity inside the marine reserves have led to reductions in macroalgal cover. Therefore, surveys compared similar reefs with significantly different macrolagal cover. Comparisons between macroalgal species revealed a four to fivefold difference in motile epifaunal densities per unit volume of macroalgae. Post‐hoc tests revealed that this difference was significant only for Lobophora, with no difference observed among the other species. As macroalgae provide both a refuge from predation and a food source for grazing epifauna, the higher densities of epifauna observed in Lobophora may be attributed to either refuge from visual predators through morphological features (high cover of overlapping blades close to the substrate) or lack of palatability for parrotfish grazing, providing a more stable refuge. Our results revealed no significant differences in diversity, density or community structure of motile epifauna per unit volume of macroalgae between sites inside and outside the ECLSP. Since canopy height and invertivore biomass did not vary systematically across reserve boundaries, this suggests that algal cover does not affect the density of epifaunal invertebrates. However, areal cover was consistently higher for all macroalgal species at sites outside the ECLSP than those inside the reserve. Therefore, when scaled by aerial cover of macroalgae, total abundance of epifauna was twofold higher outside the ECLSP. We suggest that the increasing abundance of macroalgae on Caribbean reefs may be having dramatic effects on epifaunal invertebrate populations and potentially their ecological functions.     

Reproduction in the intertidal limpet Cellana ornata in southern New Zealand

The reproductive cycle of the abundant intertidal limpet Cellana ornata (Dillwyn 1817) was examined over 19 months, covering two breeding periods, on a rocky intertidal platform in southern New Zealand. A gonad index was calculated, and histological sections were used to count the numbers of mature and immature eggs present. Fecundity was estimated using counts of eggs before and after spawning. To determine any variation between sites, the gonad index of limpets at a second site dominated by boulders was examined over 6 months during the second breeding period. C. ornata had a single spawning period annually during summer, with greatest gonad sizes in January‐February. There were significant differences in peak gonad indices between two breeding seasons on the platform. Within the second breeding period, both the timing and magnitude of peak gonad development differed between sites, with lower reproductive output at the boulder site. Fecundity increased with increasing size, but individuals are probably capable of reproducing after their first year on the shore. The life history of this species is discussed in comparison to other limpets in New Zealand.     

A holistic approach to the exploitation of intertidal stocks: limpets as a case study

The potential ecological consequences of commercially exploiting the limpets Patella argenvillei and P. granatina on the west coast of South Africa were investigated. Standing stocks were quantified and population parameters (growth, mortality and recruitment) determined for both species. These data were used to derive empirical estimates of maximum sustainable yield (MSY) for P. granatina and P. argenvillei (7,4 and 1,5 tons wet foot mass respectively). The population parameters were also used in the development of a length-based simulation model to provide a second estimate of MSY for P. granatina (up to 12,9 tons). Small-scale experimental harvesting showed that both species recovered extremely slowly if all limpets were removed (total clearance). When the harvest was size-selective (partial clearance), with P. granatina >60 mm and P. argenvillei >75 mm being removed, P. granatina failed to recover after 13 months but P. argenvillei recovered within 15 months. Partial and total clearance led to enhanced growth and survival of the remaining limpets. Partial clearance of P. granatina had no effect on other species in the community, but partial and total removal of P. argenvillei resulted in increased cover of sessile filter-feeders and macroalgae as well as a decrease in the cover of encrusting coralline algae. It is concluded that the potential exists for the development of an economically viable and ecologically sustainable fishery. Empirically derived quotas and minimum size limits of 60 mm for P. granatina and 75 mm for P. argenvillei are suggested as the chief mechanisms for regulating a potential fishery. The need for a holistic approach to the management of living (particularly intertidal) resources is stressed.     

Biological Evaluation of Marine ­Protected Area: Evidence of Crowding Effect on a Protected Population of Queen Conch in the Caribbean

Abstract This study provides a first evaluation of the biological impact of a marine fishery reserve on the stock of queen conch (Strombus gigas) in the Turks and Caicos Islands. The density and the shell length of the population living in the reserve are compared with those of the individuals living in the surrounding fished areas. The results show that the adult density is six times higher in the reserve than in the fished areas. The shell length analysis shows that both adults and juveniles are significantly smaller in the reserve than in the fished area. This unexpected result suggests the existence of a crowding effect (i. e. a high density‐induced reduction in growth rate) within the ­reserve. It is hypothesised that this crowding effect is due to the superimposition of two factors leading to very high density values in the reserve: (a) the reduced fishing mortality following the creation of the reserve, (b) the existence of natural barriers that impede the emigration of adults outside the reserve. These results are then discussed in relation to current considerations on marine fisheries reserves.     

Marine invasive aliens on South African shores: implications for community structure and tropillc functioning

Up to 12 marine mollusc and three crab species are thought to have been deliberately or accidentally introduced to South Africa. Of these, only the Mediterranean mussel Mytilus galloprovincialis and the European shore crab Carcinus meanas have become invasive. M. galloprovincialis, probably introduced in the late 1970s, is already the dominant mussel throughout the Cape west coast. As a result, indigenous intertidal mussels Aulacomya ater have been largely displaced, mussel standing stock has increased and the upshore limit of mussel beds has become considerably elevated. Implications include competitive exclusion of large limpets but enhanced recruitment of juvenile limpets, increased habitat availability for mussel infauna, reduction of habitat for algal infauna and enhanced food availability for predators, particularly terrestrial species. C. maenas was first recorded from Table Bay Docks in 1983 and currently ranges from Camps Bay to Saldanha Bay. Although it is a voracious predator, it appears unable to colonize wave-swept shores, so is unlikely to displace indigenous crabs, or to severely impact prey species on the open coast. Valuable conservation areas and mariculture sites in sheltered lagoonal areas are, however, threatened by it.     

南极菲尔德斯半岛潮间带南极帽贝的种群生态学研究──夏季种群数量变化和垂直分布

于1994年12月—1995年3月（南极夏季）期间,对南极菲尔德斯半岛卵石滩、岩石滩潮间带南极帽贝的种群数量、垂直分布进行了定点、定时、定量的调查和观察。结果表明,南极帽贝的种群数量有明显下降,分别仅为起始数量的35％和52％。卵石滩潮间带的帽贝分布于中潮区及低潮区,尤其是低潮区,且有随季节（冬季来临）向潮下带移动的趋势。岩石滩潮间带的帽贝具有类似的垂直分布特征,但其在分布带上的发生频次有很大差异,呈波动状态。在垂直岩面上,帽贝数量在低潮区的底部更为集中。讨论了导致数量变化、垂直分布的可能原因。今后有必要深入研究种群数量的时空动态及其调控机理。     

Increased predation of juvenile European spiny lobster (Palinurus elephas) in a marine protected area

One of the aims of Mediterranean marine protected areas (MPAs) is to increase populations of exploited species, such as the European spiny lobster (Palinurus elephas), which is considered a key species for its commercial and ecological value. Monitoring of temporal patterns in abundance of early benthic stages of P. elephas indicated that predation may be higher inside the Medes Islands MPA relative to adjacent control sites. Tethering experiments were performed to test whether predation rates actually differed within and outside the MPA. Relative mortality of recently‐settled juveniles inside the MPA was much higher than in control sites in adjacent non‐protected areas. Treatments with and without shelter indicated that predation on recently‐settled juvenile spiny lobsters was moderated by the availability of suitable shelter. The decline or absence of fish predators in the fished area may be the reason why juvenile lobsters outside the MPA experience lower predation than within the MPA.     

Structural, curvature and electronic properties of Rh adsorption on armchair single-walled carbon nanotube

This paper systematically studies the rolling effects of the (n, n) single-wall carbon nanotubes (SWCNT) with different curvatures on Rh adsorption behaviours by using density functional theory. The outside charge densities of SWCNTs are found to be higher than those inside, and the differences decrease with the increase of the tube radius. This electronic property led to the discovery that the outside adsorption energies are higher than the inside ones, and that the differences are reduced with the increase of the tube radius. Partial density of states and charge density difference indicate that these strong interactions induce electron transfer between Rh atoms and SWCNTs.     

Variation in population structure and life-history parameters of steentjies Spondyliosoma emarginatum: effects of exploitation and biogeography

The size and age structures, sex ratio, size- and age-at-sex-change, growth and mortality rate of the protogynous hermaphrodite, steentjie Spondyliosoma emarginatum, were compared to determine the effects on population structure and life-history parameters of exploitation (comparing an unexploited reserve and an exploited area in Langebaan Lagoon) and biogeography (comparing Langebaan Lagoon and Struisbaai on the south-west coast of South Africa). There were few large fish and a sex ratio skewed towards relatively more females in the exploited area compared with the reserve in Langebaan. The age structure of female steentjies was truncated in the exploited area but the male age structure was unaffected, possibly because of the poor relationship between size and age of males caused by accelerated growth-at-sex-change. There were no differences in the size- and age-at-sex-change between the reserve and the exploited area, suggesting that steentjies have not shown a physiological response to exploitation in Langebaan and are unable to compensate for a skewed sex ratio. The comparison between Struisbaai and Langebaan showed that the growth rate of steentjies in Struisbaai was slower and the size-at-sex-change smaller than those at Langebaan. Linefish stock assessments may have to account for regional differences in physiological parameters.     

Nutritional condition of two coastal rocky fishes and the potential role of a marine protected area

Knowledge of the nutritional conditions of coastal commercial fish populations is key to understanding stock health status, and is essential when making reasonable exploitation and management plans. Here, we present the first results on the condition and feeding preferences of two coastal fish species, Diplodus sargus (Linnaeus, 1758) and Pagellus erythrinus (Linnaeus, 1758). Using stable isotope and biochemical analyses, we tested the potential effects of a marine protected area (MPA) and the occurrence of a dramatic coastal storm on the condition and quality of nutrition. The results suggest that both condition (lipids) and nutrition quality (fatty acids, FAs) in P. erythrinus and D. sargus depend upon on food availability in the area in which they were captured. Pagellus erythrinus individuals inside the MPA stored higher quantities of lipids [46.73 ± 19.00 μg lipid·mg organic matter (OM)^?1] than those outside the MPA (15.63 ± 5.30 μg lipid·mg OM^?1) only before the storm. Diplodus sargus showed different FA signatures inside and outside the MPA before and after the storm. These results suggest that D. sargus increased their quality of nutrition inside (16.62 ± 3.17 μg FA·mg OM^?1) versus outside (7.88 ± 2.36 μg FA·mg OM^?1) the MPA, owing to increased food diversity and availability. Conversely, P. erythrinus did not show differences in nutritional quality inside (18.12 ± 1.13 μg FA·mg OM^?1) or outside (18.81 ± 1.42 μg FA·mg OM^?1) the MPA, possibly because of the increase in ingestion not affecting the studied parameters. In P. erythrinus, the FA concentration decreased after the storm, but in D. sargus, a change in lipid composition was observed. These results suggest that P. erythrinus appears to be more impacted by food quality (different saturated and unsaturated FAs) than D. sargus, owing to a more restrictive diet. We hypothesize that the observed differences between inside and outside the MPA are not only related to the degree of protection, but also to the feeding preferences and behaviour of both fishes.     

Comparative salinity tolerances of four siphonariid limpets in relation to habitat restriction of the rare and endangered Siphonaria compressa

The salinity tolerances of four South African species of limpet in the genus Siphonaria were experimentally tested, in the context that one of them, S. compressa, is South Africa's most endangered marine mollusc and is restricted to two lagoonal localities that normally experience little variation in salinity. Its habitat is additionally restricted in that it occurs only on the eelgrass Zostera capensis. The other three species, S. capensis, S. concinna and S. serrata, are abundant and widespread on temperate rocky shores. We hypothesised that S. compressa would have limited tolerance to low salinities, contributing to its absence from otherwise suitable estuaries that experience regular fluctuations of salinity. The percentage survival of the limpets was recorded in salinities ranging from 2 to 35 over that period. Both salinity and species significantly affected the survival of the limpets over the 96 hours. Survival was highest in salinities close to those of normal seawater, and greatly reduced in the hypo saline waters. S. compressa had the lowest salinity tolerance of the four species, its time-to-50% mortality in hyposaline waters being significantly less than that for the other three species, which differed in a manner that could be correlated with their zonation patterns. Restriction to eelgrass, coupled with low salinity tolerance, probably explains why S. compressa is found at only two localities, both of which normally experience salinities close to that of seawater. Even there, mass mortalities of S. compressa have been recorded in association with die-backs of eelgrass after abnormal freshwater flooding or sedimentation—further emphasising the vulnerability of S. compressa to extinction.     

Limpets as prey: Lipophrys pholis choice for size

Patellid limpets are key species on rocky shores, structuring intertidal assemblages through their grazing. Their role as prey for fish is, however, often overlooked in studies of intertidal ecosystem functioning. The shanny Lipophrys pholis is a common predator of limpets on rocky shores in Northern Europe and, in this study, we examined the characteristics of its predation on limpets based on prey size. The limpet size range that adult L. pholis (10–12.5 cm) can eat was examined in the laboratory using Patella depressa in 0.2 cm classes, varying between 0.5 cm and 3.0 cm in maximum shell length. There was a limpet size refuge above 1.8 cm, while all smaller sizes were readily consumed by the shanny. The predator attacking behaviour was also examined and found to vary with prey size. Limpets up to 0.8 cm were crushed by the jaw‐constricting force and eaten whole, whereas larger prey were prised from the substratum and the body subsequently separated from the shell. To examine whether there was a L. pholis preference for P. depressa size, a two‐stage laboratory experiment was done using two size classes defined as small (0.7–0.8 cm maximum shell length) and large (1.5–1.6 cm maximum shell length). In the first stage, the predator was given each limpet size class separately. In the second stage, the fish was given a choice between the two classes. Lipophrys pholis was shown to have a preference for the large size class (1.5–1.6 cm). The average number of limpets consumed by the shanny was examined for the duration of one high‐tide typical of the central region of Portugal (≈ 4 h). On average, approximately five limpets (up to an eight limpet maximum) were consumed. The present study shows that L. pholis has a feeding preference based on limpet size, which suggests that the limpet population structure and intra‐ and inter‐specific interactions may be influenced by the shanny predation.     

Temporal variability of sedimentation rates and mobile fauna inside and outside a gorgonian garden

Paramuricea clavata (Cnidaria, Octocorallia) is an important ecosystem engineer of coralligenous assemblages increasingly threatened by anthropogenic activities and climate changes. As climate warming is predicted to continue in the coming years it is important to hypothesize future scenarios. Here we tested the influence of gorgonian colonies on sedimentation rates and vagile fauna trends, comparing sediments collected by traps inside and outside a gorgonian garden, in a coralligenous community of the Western Ligurian Sea, at 32 m depth, over a period of 1 year. The results indicated that sea fans created a sort of homeostatic effect on the surrounding habitat. We found evidence that where gorgonian colonies were present, the monthly fluctuations of sediments rate were lower than outside a garden. Gorgonian colonies also influenced the distribution of the associated vagile fauna; these organisms were generally more abundant inside than outside the garden. The data collected in this work appear to confirm the role of P. clavata as an ecosystem engineer, affecting biomass and variability of the surrounding habitat at both spatial and temporal scales.     

Symbiosis between the holothurian Scotoplanes sp. A and the lithodid crab Neolithodes diomedeae on a featureless bathyal sediment plain

Vulnerability to predation may be high for many megafaunal taxa in deep‐sea sedimentary habitats where physical heterogeneity is low. During ROV observations in a bathyal sediment plain off Central California, juveniles of the lithodid crab Neolithodes diomedeae were frequently observed on or under the holothurian (sea cucumber) Scotoplanes sp. A, and are hypothesized to benefit from this association as a nursery or refugium from predation. Ninety‐six percent (n = 574 of 599) of the juvenile N. diomedeae observed (density varied from 0.02–0.75/m² among sites and seasons) in the study area were associated with Scotoplanes sp. A. Of the 2596 Scotoplanes sp. A observed (density varied from 0.48 to 25.90/m²), 22% were attended by at least one juvenile crab, and rarely two crabs (n = 4). Solitary N. diomedeae were rarely observed. This decapod–holothurian symbiosis appears to be largely commensal, with juvenile crabs (carapace width = 0.03–0.31 ×  holothurian length) observed on or beneath Scotoplanes sp. A in a habitat with few refugia from epibenthic predators. Other hypotheses may explain or enhance the potential benefits of the association for N. diomedeae, such as elevated food availability due to the activities of Scotoplanes sp. A. The relationship may be mutualistic if there is a benefit for the holothurian, including the removal of epizoic parasites. Ultimately, the nursery or other effects on the population dynamics of N. diomedeae may be minimal in low‐relief, sediment‐dominated habitats, as very few sub‐adult crabs were observed in the study area and were likely consumed upon outgrowing their refugia. While sedimentary habitats may be a sink for N. diomedeae populations, growth of juvenile crabs during their association with Scotoplanes sp. A should increase energy flow to its predator populations. This association has not been reported previously but may be expected in sediment‐dominated habitats where these species overlap.     

Biology of evechinus chloroticus (echinoidea: Echinometridae) from different localities

The distribution, general habits, morphological variation, food, associates and predators ‘Of the common endemic New Zealand echiooid Evechinus chloroticus (Val.) are considered.

Evechinus chloroticus is chiefly a rocky bottom dweller but adults, juveniles and very small individuals often occupy different microhabitats. The urchin is typically found in shallow subtidal situations (<12m) although considerable intertidal populations occur in some areas, particularly towards the north. A superimposed dispersion pattern of population and intra‐population clumping is typical and densities often exceed 50 adults/m².

Spine length, thickness and sharpness and test thickness vary between populations but no significant variation in test shape (height/diameter) was observed. Variations in spination are probably related to wave exposure while test thickness is at least in part related to nutrition.

In the localities where macroscopic algae are diverse and abundant, Evechinus is almost exclusively algivorous, but it predominantly browses material from the substrate where algae are sparse.

The rhabdocoele, Syndesmis sp. (in the gut) and various tiliates (in the gut and gonad) were commonly found in Evechinus. The urchin provides shelter and food for the clingfish Dellichthys morelandi, and the isopod Exosphaeroma sp. is probably also a close associate.

Known predators include the cymaitiid gastropods Charonia capax and C. rubicunda, the seastar Coscinasterias calamaria, and the blue cod Parapercichthys colias and snapper Chrysophrys auratus.     

The impact of commercial and recreational harvesting for Paracentrotus lividus on shallow rocky reef sea urchin communities in North-western Sardinia, Italy

The fishery for the edible sea urchin Paracentrotus lividus is of great importance to many European regions, although in some of them this species has shown a wide scale decline in recent years. This paper reports on direct (on P. lividus) and indirect (on the co-occurring but not fished echinoid, Arbacia lixula) effects of sea urchin harvesting in shallow rocky reefs in North-western Sardinia (Italy, central-western Mediterranean Sea), where this activity is intensively practised. Density, size (test diameter), and biomass of both species were assessed in autumn 2004 at two locations impacted by P. lividus fishery, and at two controls within an adjacent Marine Protected Area. Density of P. lividus and A. lixula was significantly greater at the controls than at the exploited locations. The average test diameter of P. lividus was also significantly larger at the controls, where large-sized specimens (i.e. >5 cm) were notably more abundant. The average size of A. lixula did not significantly differ between the impacted locations and the controls. The average biomass of P. lividus was significantly greater at the controls than at the exploited locations, whereas no differences were detected for A. lixula. These results reveal the existence of a heavy fishing impact on P. lividus in North-western Sardinia and the need for regulation of its harvesting to prevent severe direct effects on its populations. Since no indirect effects on A. lixula have been detected, it could be hypothesized that this species did not benefit from P. lividus fishery due to an only moderate competition for habitat and resources between these two echinoids. Implications for management of edible sea urchin fishery are also discussed.     

Effects of Paracentrotus lividus (Lamark, 1816) harvesting on benthic assemblages. An experimental approach

The effect of harvesting on the diversity and structure of benthic assemblages is nowadays a relevant component of fishery management. Invertebrate harvesting is increasing worldwide and sea urchins are one of the main invertebrate target species. However, current knowledge about the effects of sea urchin harvesting on benthic assemblages is still poor. The aim of this study is to evaluate the influence of Paracentrotus lividus (Lamark, 1816) harvesting on tide pool assemblages from intertidal rocky shores. To achieve this objective, a field removal experiment was done for 10 months. Results of univariate and multivariate analyses showed that P. lividus harvesting had a significant effect on the number of taxa and structure of the benthic assemblage. Assemblages from pools where P. lividus were removed showed significant differences against controls; namely, where P. lividus were eliminated, pools showed higher number of taxa than control pools. This result contrasts with previous studies assessing effects of invertebrate harvesting that generally have found a biodiversity reduction in the exploited habitat. Despite this apparently positive effect of P. lividus harvesting, we should be cautious because effects of P. lividus harvesting on higher trophic levels or during long periods of time remain unexplored.     

Biomass and production of bacterioplankton at the hydrothermal vent areas in the rift system of the North Fiji Basin

Mesoscale distribution of the density and productivity of bacterioplankton at representative geological locations in the rift ecosystem of the North Fiji Basin were clarified by sampling using a mannedShinkai 6500 submersible. The bacterioplankton density inside the hot and warm fluids of hydrothermal vents was one order magnitude greater than that in the deep water outside the vent plume. The bacterial production was highest inside the hot and warm vent fluids, and was higher just outside the hot and warm vent fluids than further outside in the deep water surrounding the vent plume, respectively. Productivity from outside to inside the vent fluid varied from 0.01 to 0.71 gC m^–3 day^–1.