Deep-water Populations Research Articles

Age, Growth, and Population Structure of Conomurex luhunuas

Age and growth dynamics of Conomurex luhuanus were investigated to determine the population structure. Age-specific change in shell shape determined with geometric morphometrics revealed discrimination of shape between 0-3 years old at 99–100% while 3–4 years old can be separated with 81% certainty. Using the age discrimination data, K and L∞ were estimated at 1.00 year-1 and 7.28 cm, respectively. Recruitment is bimodal with natural mortality (M) of 0.71 and fishing mortality (F) approximated at 3.92 year-1. The exploitation rate (E) is 0.85 year-1, indicating probable overharvesting of the population under study. The presence of a deep-water population, age-specific burying behavior, and bimodal recruitment pattern are possible resilience factors.

Size-distribution and length-weight relationship of a deep-water population of Holothuria scabra (Jaeger, 1833) in Zanzibar, Tanzania

A study was carried out on the size distribution, length-weight relationship and condition factor of a deep-water population of the commercially important tropical sea cucumber Holothuria scabra in Zanzibar, Tanzania. Samples were collected from fishers and supplementary information gathered. The deep water (15-20 m) population of H. scabra is dominated by large sized individuals that have already attained maturity. There was no significant difference in size between male and female individuals (p>0.05). The sex ratio in this population significantly differed from 1:1 in favour of male individuals (p=0.01). The results showed significant correlation between length and weight for male, female, indeterminate individuals, and pooled data, with r values of 0.681, 0.794, 0.821 and 0.680, respectively. Moreover, the b-value for male, female, indeterminate individuals and pooled data was 1.288, 1.439, 1.686 and 1.407 respectively, which revealed that individuals of deep-water H. scabra exhibit negative allometric growth. The mean condition factor (K) value when all data were pooled together was 4.213±0.106 indicating that individuals were in good condition and came from a healthy environment. This study fills a key information gap that is relevant to the management of the H. scabra fishery in the country.

Testing the efficacy of lionfish traps in the northern Gulf of Mexico.

Spearfishing is currently the primary approach for removing invasive lionfish (Pterois volitans/miles) to mitigate their impacts on western Atlantic marine ecosystems, but a substantial portion of lionfish spawning biomass is beyond the depth limits of SCUBA divers. Innovative technologies may offer a means to target deepwater populations and allow for the development of a lionfish trap fishery, but the removal efficiency and potential environmental impacts of lionfish traps have not been evaluated. We tested a collapsible, non-containment trap (the 'Gittings trap') near artificial reefs in the northern Gulf of Mexico. A total of 327 lionfish and 28 native fish (four were species protected with regulations) recruited (i.e., were observed within the trap footprint at the time of retrieval) to traps during 82 trap sets, catching 144 lionfish and 29 native fish (one more than recruited, indicating detection error). Lionfish recruitment was highest for single (versus paired) traps deployed <15 m from reefs with a 1-day soak time, for which mean lionfish and native fish recruitment per trap were approximately 5 and 0.1, respectively. Lionfish from traps were an average of 19 mm or 62 grams larger than those caught spearfishing. Community impacts from Gittings traps appeared minimal given that recruitment rates were >10X higher for lionfish than native fishes and that traps did not move on the bottom during two major storm events, although further testing will be necessary to test trap movement with surface floats. Additional research should also focus on design and operational modifications to improve Gittings trap deployment success (68% successfully opened on the seabed) and reduce lionfish escapement (56% escaped from traps upon retrieval). While removal efficiency for lionfish demonstrated by traps (12-24%) was far below that of spearfishing, Gittings traps appear suitable for future development and testing on deepwater natural reefs, which constitute >90% of the region's reef habitat.

The intra-population variability of a freshwater crustacean Polyphemus pediculus (Cladocera, Onychopoda)

A discriminant canonical analysis was employed to study the morphometric structure of a shallow-water local population during the open-water period, and of an autumn deep-water local population extending from the depths of 1.2 m to 23.6 m. Statistically treated data on 11 quantitative and 12 meristic features of 505 mature individuals from the shallow-water population and 294 specimens from the deep-water population were analyzed in the study. P. pediculus belongs to an ecologically polymorphic species. The morphometric structure of local populations of the species and its peculiarities are governed by the environmental conditions of the habitat and have an adaptive value. The population structure is unstable, subject to spatial and temporal variations together with the biotopic and seasonal variations of the environment. A continuous sympatric speciation proceeding in the populations leads to the formation of a number of phenotypes adapted to the existence in specific sub-niches. The morphometric structure of the shallow-water population is formed by three short-term seasonal races having statistically significant differences, and following in succession in correspondence with the change of season. Their morphometric diversity and variability reduce from spring to autumn; the highest statistically significant differences are peculiar to the autumn race. Crustaceans of the summer months do not display statistically significant differences between each other. Morphometric differences between seasonal races do not exceed the limits of the species variability range, and are conditioned mainly by variations in the total length of Ant II and in the number of setae in the medial rows of thoracic limbs of the I-III pairs. The morphometric structure of the deep-water population is more complex and stable, and is formed by three permanent morphoforms, which differ statistically significantly from each other and exist at different depths: the main (1.2–4.7 m), the intermediate (9.3 m) and the deep water (23.6 m). The degree and the accuracy of differences between the morphoforms increase with the depth of habitation. Permanent biotopic races are present at different depths within the morphoforms. The races of the intermediate and the deep-water morphoforms differ statistically significantly from the races of the main morphoform. The races of the main morphoform do not have any statistically significant differences between them. The number of crustaceans permanently present within the biotopic races increases with the habitation depth, and the number of individuals performing vertical migrations reduces. The deep-water morphoform is the most isolated and stable. A considerable divergence of quantitative features is observed in the specimens of this morphoform, resulting in the formation of a new species P. deepwater. Morphometric differences of the biotopic races are conditioned mainly by variations in the total length of Ant II, the length of the caudal stem and setae, Ant I free segments, the head diameter, and the number and length of setae on the third segments of endopodites of thoracic limbs of the I-III pairs.

A New Species of Forreria (Gastropoda: Muricidae: Ocenebrinae) from the Sea of Cortez, Mexico

A new muricid is described from deep water in the Wagner Basin, in the northern Sea of Cortez, Mexico, 65 kilometers south of Puerto Peňasco, Sonora, Mexico. The only living relative of this new species is Forreria belcheri (Hinds, 1843), which ranges from Santa Barbara, California, to Laguna Scammons, Baja California, Mexico. This new endemic species has been brought to light by shrimp trawling activities, and is thought to be a relict deep water population left behind in the northern Sea of Cortez during the Pleistocene.

Population genetics of Narella versluysi (Octocorallia: Alcyonacea, Primnoidae) in the Bay of Biscay (NE Atlantic)

Octocoral species are globally distributed in all oceans and may form dense communities known as vulnerable marine ecosystems. Despite their importance as deep-water habitats, the underlying genetic structure and gene-flow patterns of most deep-water populations remain largely unknown. Here, we evaluated genetic connectivity of the primnoid octocoral Narella versluysi across the continental shelf of Bay of Biscay, spanning 360 km (95 samples from submarine canyons, ranging from 709–1247 m depths). We report 12 novel microsatellite markers which were used to genotype 83 samples from 6 populations. Sixteen samples were sequenced for three mitochondrial DNA regions (Folmer region of COI with an adjacent intergenic region igr1, MT-ND2 gene, and mtMutS homolog 1 region). All sequence haplotypes and genetic clusters were found in multiple sites spanning more than 200 km. Overall, our analyses suggest that there is high gene flow between colonies of N. versluysi among all study sites. There is no significant geographic structure and no pattern of isolation by distance or depth. Connectivity is facilitated by the prevailing current which runs along the shelf break, and could be a mechanism to connect all of the sampled locations. The high connectivity over large geographic distance is a positive sign for a potentially vulnerable organism and may provide some resilience to disturbance. This information is crucial for a better understanding of how this fragile benthic fauna may respond to climatic and anthropogenic disturbances, which is a cornerstone for effective habitat management.

Characterisation of a deep-water moss from the perennially ice-covered Lake Vanda, Antarctica

Bryophytes from submerged habitats are particularly difficult to identify because developmental plasticity obscures their characteristic features. A deep-water moss population of uncertain identity was found isolated at a depth of 31 m within the perennially ice-covered Lake Vanda, Wright Valley, Antarctica. Through phylogenetic analysis of the chloroplast region, ribosomal subunit 4 gene, nuclear ribosomal DNA region, and the internal transcribed spacer region, the Lake Vanda moss was identified as the cosmopolitan species Bryum pseudotriquetrum and resolved to a clade containing exclusively specimens from Antarctica, specifically those from the neighbouring Taylor Valley and Granite Harbour. The close genetic similarity of the Lake Vanda population to other populations of B. pseudotriquetrum in Southern Victoria Land suggests that colonisation was likely to have been from local sources, and colonisation likely occurred at least 80–100 years ago, given the position of mosses in the deeper of two convection cells in the lake. Light and scanning electron microscopy of in vitro cultured specimens revealed adaptations to permanent submersion, including very thin cell walls, which may increase CO2 absorption under water. The production of rhizoidal knots in contaminated, low-nutrient media, but not in axenic cultures, might result from interactions between the moss and organisms in the microbial mat from which it was isolated. The absence of mosses around the lake margin or elsewhere in Wright Valley highlights the importance of freshwater ecosystems as refugia for biodiversity in Antarctica.

Stress physiology and reproductive phenology of Arctic endemic kelp Laminaria solidungula J. Agardh

The reproductive phenology and the responses of the early life history stages of the Arctic endemic kelp Laminaria solidungula to global climate change stressors were investigated. This species inhabits low-light areas at depths up to 18 m and under the canopy of other large kelps in shallower depths. Around Svalbard, fertile sporophytes had been collected in late spring to early autumn. This observation suggests that sporogenesis starts in late autumn, continuing throughout the winter and ending in early spring, or that reproduction may occur throughout the year, especially among deepwater population where diel fluctuating low light may be perceived as short days to induce sporogenesis. Fertile sporophytes were induced to release spores that were subsequently exposed to different temperatures (2, 7, 12, 17 °C) in isolation and in interaction with ultraviolet radiation (UVR). Results showed a high temperature affinity up to 12 °C for meiospore germination and growth, but its photosynthesis was low-light-adapted and susceptible to UVR. After 16 days of cultivation, germlings died under 17 °C and gametophyte size was largest at 12 °C. After 48-day cultivation under continuous daylight, gametogenesis was not observed. The projected ocean warming will unlikely negatively affect photosynthesis and growth of micro- and macrostages of L. solidungula. Conversely, the susceptibility of meiospores and gametophytes to high PAR and UVR can disrupt the completion of the life cycle. However, sporogenesis and gametogenesis, which are the key processes for the survival of this Arctic endemic species that requires low temperature and short days, can still occur in deepwater habitats.

Biological source and provenance of deep-water derived isoprenoid tetraether lipids along the Portuguese continental margin

There is increasing evidence that nitrifying Thaumarchaeota in the deep ocean waters may contribute to the sedimentary composition of isoprenoid glycerol dialkyl glycerol tetraethers (isoGDGTs), impacting TEX86 paleothermometry. We investigated the potential effect of deep-water dwelling Thaumarchaeota in the warm and saline Mediterranean Outflow Water (MOW) on the distribution of isoGDGTs by analysing suspended particulate matter (SPM) and surface sediments collected along five land-ocean transects along the southern Portuguese continental margin. To this end, we directly compared for the first time the composition of intact polar lipid (IPL)-derived isoGDGTs of SPM with the diversity, abundance, and activity of Thaumarchaeota based on the genetic analysis of the genes coding for the archaeal ammonia monooxygenase (amoA) and the geranylgeranylglyceryl phosphate (GGGP) synthase involved in the isoGDGT biosynthetic pathway. Our results revealed a strong positive relationship between water depth and TEX86H values for both SPM and surface sediments. The increasing TEX86H trends for both core lipid (CL) and IPL-derived fractions were accompanied by increasing fractional abundances of GDGT-2 and crenarchaeol regio-isomer and decreasing fractional abundances of GDGT-1 and GDGT-3 with increasing water depth. Phylogenetic analyses based on the archaeal amoA and the GGGP synthase proteins showed that Thaumarchaeota populations detected at 1m and 50m water depth were different from those detected in 200m and 1000m water depth, which had an increased contribution of so-called ‘deep water’ Thaumarchaeota. The differences in the fractional abundances of isoGDGTs with water depth were compatible with the increasing contribution of ‘deep water’ Thaumarchaeota harboring a different GGGP synthase enzyme which has been suggested to relate to changes in the relative proportion of synthesized isoGDGTs. Accordingly, it appears that the sedimentary distribution of CL isoGDGTs used in TEX86H along the Portuguese margin is primarily influenced by water depth due to the increasing contribution of the deep-water population of Thaumarchaeota residing in the MOW. Our study also reveals that the effect of deep water Thaumarchaeotal communities on sedimentary isoGDGT distributions should be considered globally.

Differential responses of coral larvae to the colour of ambient light guide them to suitable settlement microhabitat.

Reef-building corals produce planktonic planula larvae that must select an appropriate habitat to settle and spend the rest of their life, a behaviour that plays a critical role in survival. Here, we report that larvae obtained from a deep-water population of Pseudodiploria strigosa settled more readily under blue light and in the dark, which aligns well with the light field characteristics of their natal habitat. By contrast, larvae of the shallow-water coral Acropora millepora settled in high proportions under blue and green light while settlement was less in the dark. Acropora millepora larvae also showed reduced settlement under red light, which should be abundant at shallow depth. Hypothesizing that this might be a mechanism preventing the larvae from settling on the exposed upwards-facing surfaces, we quantified A. millepora settlement in manipulated light chambers in situ on the reef. While A. millepora larvae naturally preferred settling on vertical rather than exposed horizontal surfaces, swapping the colours of upwards-facing and sideways-facing light fields was sufficient to invert this preference. We also tested if the variation in intrinsic red fluorescence in A. millepora larvae correlates with settlement rates, as has been suggested previously. We observed this correlation only in the absence of light, indicating that larval red fluorescent protein is probably not directly involved in light sensing. Our study reveals previously under-appreciated light-sensory capabilities in coral larvae, which could be an important axis of ecological differentiation between coral species and/or populations.

A depth refugium from catastrophic coral bleaching prevents regional extinction.

Species intolerant of changing climate might avoid extinction within refugia buffered from extreme conditions. Refugia have been observed in the fossil record but are not well documented or understood on ecological time scales. Using a 37-year record from the eastern Pacific across the two most severe El Niño events on record (1982-1983 and 1997 1998) we show how an exceptionally thermally sensitive reef-building hydrocoral, Millepora intricata, twice survived catastrophic bleaching in a deeper-water refuge (> 11 m depth). During both events, M. intricata was extirpated across its range in shallow water, but showed recovery within several years, while two other hydrocorals without deep-water populations were driven to regional extinction. Evidence from the subfossil record in the same area showed shallow-water persistence of abundant M. intricata populations from 5000 years ago, through severe El Niño-Southern Oscillation cycles, suggesting a potential depth refugium on a millennial timescale. Our data confirm the deep refuge hypothesis for corals under thermal stress.

Single-cell genomics shedding light on marine Thaumarchaeota diversification

Previous studies based on analysis of amoA, 16S ribosomal RNA or accA gene sequences have established that marine Thaumarchaeota fall into two phylogenetically distinct groups corresponding to shallow- and deep-water clades, but it is not clear how water depth interacts with other environmental factors, including light, temperature and location, to affect this pattern of diversification. Earlier studies focused on single-gene distributions were not able to link phylogenetic structure to other aspects of functional adaptation. Here, we analyzed the genome content of 46 uncultivated single Thaumarchaeota cells sampled from epi- and mesopelagic waters of subtropical, temperate and polar oceans. Phylogenomic analysis showed that populations diverged by depth, as expected, and that mesopelagic populations from different locations were well mixed. Functional analysis showed that some traits, including putative DNA photolyase and catalase genes that may be related to adaptive mechanisms to reduce light-induced damage, were found exclusively in members of the epipelagic clade. Our analysis of partial genomes has thus confirmed the depth differentiation of Thaumarchaeota populations observed previously, consistent with the distribution of putative mechanisms to reduce light-induced damage in shallow- and deep-water populations.

Morphology and phytogeography of Laminaria appressirhiza and L. inclinatorhiza (Phaeophyceae) from the Sea of Okhotsk

The re-examination of morphological and anatomical characters of Laminaria appressirhiza and L. inclinatorhiza collected from different localities in the Sea of Okhotsk was performed. Despite their commercial and ecological importance to the region they have not been comprehensively reviewed since their first description in 1970. Our results show that some original diagnostic key characters (e.g., shape of holdfast, shape of sporangial sori, and dissection of blade) are not stable and have deviations from the type morphology when plants grow in different environments. In L. inclinatorhiza, the sporangial sori development occurred differently to the pattern indicated in original species description as they did not develop simultaneously on both sides of the blade. Instead, the sporangial sori outlines on both sides of the blade did not coincide at first and only became coincident later. Also, a deep-water population of L. inclinatorhiza with an unusual and interesting morphology, growing at depths of 15-25 m on opened rocky coasts in Taujskaya Bay (northern part of the Sea of Okhotsk) was found. The stable diagnostic key characters to distinguish these two species are the cone-like, multilayered, very thick and massive holdfast (in L. inclinatorhiza) and rolled margins of blades, lamellar rosette-like part of thallus, and sporangial sori developing only on one side of the blade (in L. appressirhiza). The ecological characteristics, distribution, and abundance of both species in the Sea of Okhotsk are discussed. Both species are perennial and widely distributed in the region. L. appressirhiza is more often found as a subdominant species among other kelps, forming maximum biomass and density of 7-9 kg and 8-25 plants per , respectively. L. inclinatorhiza sometimes forms local mono-species communities with maximum biomass and density of 10-12 kg and 10-15 plants per , respectively.

Spatial and temporal variability of deep-water algal assemblages in the Northwestern Mediterranean: The effects of an exceptional storm

There are deep-water populations of the endemic and threatened Mediterranean brown alga Cystoseira zosteroides in the Medes Islands Marine Reserve (NW Mediterranean). Here, the distribution, population structure, individual growth, mortality and recruitment rates of this species over two years are described in relation to the effects of an exceptional storm. We found a high spatial variability in the structure and dynamics of C. zosteroides populations at small geographical scales, suggesting that environmental factors acting at the population level display a key role in population size structure, mortality and recruitment. The elevated mortality rates recorded at some locations (almost 80%) is amongst the highest recorded for perennial algae as a consequence of a single storm, emphasizing the importance of episodic catastrophic events in the maintenance of these deep-water, slow-growing populations. These findings are of particular importance not only to fully understand the ecology of C. zosteroides, but also for its conservation.

Improving marketability through translocation: a lobster case study from southern Australia

Abstract Chandrapavan, A., Gardner, C., Green, B. S., Linnane, A., and Hobday, D. 2011. Improving marketability through translocation: a lobster case study from southern Australia. – ICES Journal of Marine Science, 68: 1842–1851. Translocation as a method to increase the value of less-marketable, deep-water southern rock lobster Jasus edwardsii was explored. First, variation in the commercially important shell colouration and body shape between deep- and shallow-water Tasmanian populations and among South Australian and Victorian populations was quantified. Deep-water J. edwardsii were pale in colour, with longer walking legs but less meat content than shallow-water, red-coloured J. edwardsii. Traits in body shape were variable among deep-water populations across the three states and between sexes in each population. Deep-water lobsters were then translocated to a shallow-water inshore reef to determine whether the observed variation in traits was plastic and whether translocation could be used to improve the quality of deep-water lobsters. Translocated lobsters were then monitored over a 14-month post-release period, and during this time, they changed from a pale/white colour to the more marketable red colour within a single moult. Plasticity was observed in tail morphology, but not in leg morphology. The translocation experiment was successful in transforming pale/white deep-water lobsters into red lobsters with higher market value in a phenotypic response to habitat manipulation. Translocation appears to have commercial application for exploiting natural plasticity in the market traits of lobsters to increase price.

Two Northeast Pacific deep-water barnacle populations (Cirripedia: Calanticidae and Pachylasmatidae) from seamounts of the Juan de Fuca Ridge; "insular" endemics stemming from Tethys, or by subsequent dispersal from the Western Pacific center of distribution?

The first adults of the calanticid, Calantica moskalevi Zevina and Galkin, 1989, and specimens of a new pachylasmatine balanomorph genus and species, have been recovered by MBARI’s ROV Tiburon, from Juan de Fuca Ridge seamounts at ~46º N – 130º W in the NE Pacific off Oregon, ~1450 m and 2080 m depths, respectively. These two apparently allopathic populations evidently represent remnants of stocks most commonly confined to relatively deep waters around islands and occasionally continental margins of the Indo-West Pacific. These Juan de Fuca representatives can be inferred to be relicts of once broad Paleogene Tethyan populations rather than relatively recent immigrants by way of the NW Pacific. Apparently, the refugium afforded by seamount “islands” at bathyal and abyssal depths accounts for their survival in this relatively remote corner of Pacific Oceania.

Quantifying the decline in Corallium rubrum populations

A recent article by Bruckner (2009; Mar Ecol Prog Ser 397:319-332) focused on popula- tion decline in the commercially exploited Mediterranean red coral Corallium rubrum. Bruckner (2009) used data on coral size structure and reproductive output gathered by a variety of sampling methods in different populations: Data on overharvested shallow-water populations (which are gen- erally made up of crowded, small-sized colonies) were combined with the small amount of data avail- able on deep-water populations (which consist of larger, sparse colonies); the latter have become the main target for commercial harvesting nowadays. In our opinion, the conclusions in Bruckner (2009) did not fully reflect the heterogeneity and the limits of the data set. Collection of sound demographic data through broader, coordinated research applying standard procedures to different populations is required for a reliable analysis of Corallium rubrum population dynamics.

A shallow water population of Pronotogrammus martinicensis (Guichenot, 1868) (Teleostei: Serranidae: Anthiinae) from South-western Atlantic, Brazil

A population of Pronotogrammus martinicensis (Guichenot, 1868) is described and recognized as a unique shallowwater variation of the species from the Brazilian South-Eastern coast, based on genetic, morphologic and ecological data. It is distinguished from the deep water population by its smaller eye, longer snout, shorter pectoral-fin, color of the adults, and habitat depth.

Temporal and spatial variability in shallow- and deep-water populations of the invasive Caulerpa racemosa var. cylindracea in the Western Mediterranean

The invasive green alga Caulerpa racemosa var. cylindracea represents an important threat to the diversity of Mediterranean benthic coastal ecosystems by interfering with native species and modifying benthic assemblages. The present study deals, for the first time, with the temporal and spatial variability of the biomass and phenology of C. racemosa considering both deep- and shallow-water populations. Two sampling depths (30 and 10 m) were sampled at three different rocky bottom sites every 3 months in the Archipelago of Cabrera National Park (Western Mediterranean). All morphometric variables analysed showed a spatial variation and temporal patterns depending on depth. Between depths, C. racemosa biomass, stolon length, number of fronds and frond length were usually significantly higher at deep-water populations, suggesting that C. racemosa grows better in deep-waters. Deep- and shallow-water populations displayed a high temporal variation although no evidence of seasonal patterns was found, in contrast with what has been reported by other authors. The sources of this variability are still unknown but probably both physical factors and differential herbivory pressures display a key role.

Molluscs associated with a Sardinian deep water population of Corallium rubrum (Linnι, 1758)

Molluscan species living in association with Corallium rubrumcolonies are poorly known. Specimensfound on the branches of red coral colonies located off Capo Caccia (Alghero – SS, West Sardinia,Mediterranean Sea) were studied by analyzing red coral branches collected at a depth of between 100 and120 m; their assemblage was made up of 44 species, all belonging to the classes Gastropoda and Bivalvia.Some data on the geographical distribution, ecology, taxonomy and dominance of these species, bothalive and dead, are given and the most interesting are commented on. Among the recorded species Triviamultilirata, Simnia purpurea, Coralliophila brevis, Ocinebrina paddeui, Pleurotomella demosia, Palliolumstriatum and Pseudamussium sulcatum deserve attention. Moreover, the second finding of livingspecimens of Asperarca secreta, described only on loose valves, is reported, and finally the prey-predatorrelationships among several gastropods and Cnidarians are confirmed.