Shallow-water Marine Habitats Research Articles

Aftereffects of Hurricanes Irma and Ian on queen conch Aliger gigas in the Florida Keys, USA

Hurricanes can have substantial impacts on shallow-water marine habitats and species. Populations of slow-moving benthic species that are subject to depensation such as the queen conch Aliger gigas may be particularly vulnerable to hurricanes. The species is protected in Florida (USA), which allowed us to investigate the effects of Hurricanes Irma (2017) and Ian (2022) on the population without the confounding effects of fishing. Adult queen conch density had declined over 80% at sites resurveyed immediately after the passage of Hurricane Irma. Additionally, the sites closest to the eye of Hurricane Irma had a significant increase in the percent cover of sand. The sand mobilized by the storm likely buried numerous conch and caused mortality. Subsequent Florida Keys-wide annual monitoring did not show any substantial recovery in adult density prior to Hurricane Ian. Adult density had declined by ~45% at sites resurveyed after Hurricane Ian. Unlike after Irma, we did not detect any significant correlation in the change to the percent cover of sand with distance from Ian. This was probably because the eye of Hurricane Ian was farther away from the main portion of the Keys than that of Hurricane Irma. Nevertheless, after both hurricanes, adult density dropped below the minimum threshold for mating in the Keys, demonstrating the depensatory implications of hurricanes for conch populations. Consequently, fishery managers must consider the synergistic effects of hurricanes and harvest on exploited populations, especially since the intensity, longevity, and frequency of hurricanes are expected to increase due to climate change.

Checklist of the shallow-water marine Brachyura (Crustacea: Decapoda) of Barbados, West Indies.

Here we provide an illustrated and annotated checklist of brachyuran crabs associated with shallow water marine habitats (nearshore rubble and subtidal) in Barbados, West Indies (13.1939°N, 59.5432°W). Twenty-one (21) survey sites in nearshore rubble and shallow subtidal habitats were surveyed between October 2018 to September 2021. Nearshore rubble habitats were surveyed at low tide during the day and night periods. Shallow nearshore subtidal habitats were surveyed every 9-12 days from February to October 2019 using crab traps placed ~ 4 m deep on sandy and rocky bottoms. A total of 1,640 specimens were recorded, belonging to nine (9) superfamilies, 14 families, 34 genera, and 44 species. The genera Charybdis De Haan, 1833, Pitho Bell, 1835, Thoe Bell, 1835, and Uhlias Stimpson, 1871 are here reported for the first time for Barbados. Thirteen (13) species are first records for Barbados, thus extending their geographic range. The most abundant and widespread species collected was Mithraculus coryphe Herbst, 1801, which accounted for 35% (N = 570) of the specimens, occurring in both nearshore rubble and subtidal habitats.

Diel CO2 cycles and parental effects have similar benefits to growth of a coral reef fish under ocean acidification.

Parental effects have been shown to buffer the negative effects of within-generation exposure to ocean acidification (OA) conditions on the offspring of shallow water marine organisms. However, it remains unknown if parental effects will be impacted by the presence of diel CO2 cycles that are prevalent in many shallow water marine habitats. Here, we examined the effects that parental exposure to stable elevated (1000 µatm) and diel-cycling elevated (1000 ± 300 µatm) CO2 had on the survival and growth of juvenile coral reef anemonefish, Amphiprion melanopus. Juvenile survival was unaffected by within-generation exposure to either elevated CO2 treatment but was significantly increased (8%) by parental exposure to diel-cycling elevated CO2. Within-generation exposure to stable elevated CO2 caused a significant reduction in juvenile growth (10.7-18.5%); however, there was no effect of elevated CO2 on growth when diel CO2 cycles were present. Parental exposure to stable elevated CO2 also ameliorated the negative effects of elevated CO2 on juvenile growth, and parental exposure to diel CO2 cycles did not alter the effects of diel CO2 cycles on juveniles. Our results demonstrate that within-generation exposure to diel-cycling elevated CO2 and parental exposure to stable elevated CO2 had similar outcomes on juvenile condition. This study illustrates the importance of considering natural CO2 cycles when predicting the long-term impacts of OA on marine ecosystems.

Biomineralization in bryozoans: present, past and future.

Many animal phyla have the physiological ability to produce biomineralized skeletons with functional roles that have been shaped by natural selection for more than 500 million years. Among these are bryozoans, a moderately diverse phylum of aquatic invertebrates with a rich fossil record and importance today as bioconstructors in some shallow-water marine habitats. Biomineralizational patterns and, especially, processes are poorly understood in bryozoans but are conventionally believed to be similar to those of the related lophotrochozoan phyla Brachiopoda and Mollusca. However, bryozoan skeletons are more intricate than those of these two phyla. Calcareous skeletons have been acquired independently in two bryozoan clades - Stenolaemata in the Ordovician and Cheilostomata in the Jurassic - providing an evolutionary replicate. This review aims to highlight the importance of biomineralization in bryozoans and focuses on their skeletal ultrastructures, mineralogy and chemistry, the roles of organic components, the evolutionary history of bimineralization in bryozoans with respect to changes in seawater chemistry, and the impact of contemporary global changes, especially ocean acidification, on bryozoan skeletons. Bryozoan skeletons are constructed from three different wall types (exterior, interior and compound) differing in the presence/absence and location of organic cuticular layers. Skeletal ultrastructures can be classified into wall-parallel (i.e. laminated) and wall-perpendicular (i.e. prismatic) fabrics, the latter apparently found in only one of the two biomineralizing clades (Cheilostomata), which is also the only clade to biomineralize aragonite. A plethora of ultrastructural fabrics can be recognized and most occur in combination with other fabrics to constitute a fabric suite. The proportion of aragonitic and bimineralic bryozoans, as well as the Mg content of bryozoan skeletons, show a latitudinal increase into the warmer waters of the tropics. Responses of bryozoan mineralogy and skeletal thickness to oscillations between calcite and aragonite seas through geological time are equivocal. Field and laboratory studies of living bryozoans have shown that predicted future changes in pH (ocean acidification) combined with global warming are likely to have detrimental effects on calcification, growth rate and production of polymorphic zooids for defence and reproduction, although some species exhibit reasonable levels of resilience. Some key questions about bryozoan biomineralization that need to be addressed are identified.

New species of Floresorchestia from Micronesia living in unusual habitats (Crustacea, Amphipoda, Talitridae).

The first freshwater talitrid, Floresorchestia pohnpei sp. nov., is described from the island of Pohnpei, Micronesia. Floresorchestia palau sp. nov. is described from supralittoral and shallow-water marine habitats in Palau, Micronesia.

Heading for new shores: projecting marine distribution ranges of selected larger foraminifera.

The distribution of modern symbiont-bearing larger foraminifera is confined to tropical and subtropical shallow water marine habitats and a narrow range of environmental variables (e.g. temperature). Most of today's taxa are restricted to tropical and subtropical regions (between 30°N and 30°S) and their minimum temperature limits are governed by the 14 to 20°C isotherms. However, during times of extensive global warming (e.g., the Eocene and Miocene), larger foraminifera have been found as far north as 50°N (North America and Central Europe) as well as towards 47°S in New Zealand. During the last century, sea surface temperatures have been rising significantly. This trend is expected to continue and climate change scenarios for 2050 suggest a further increase by 1 to 3°C. We applied Species Distribution Models to assess potential distribution range changes of three taxa of larger foraminifera under current and future climate. The studied foraminifera include Archaias angulatus, Calcarina spp., and Amphistegina spp., and represent taxa with regional, superregional and global distribution patterns. Under present environmental conditions, Amphistegina spp. shows the largest potential distribution, apparently due to its temperature tolerance. Both Archaias angulatus and Calcarina spp. display potential distributions that cover currently uninhabited regions. Under climate conditions expected for the year 2050, all taxa should display latitudinal range expansions between 1 to 2.5 degrees both north- and southward. The modeled range projections suggest that some larger foraminifera may colonize biogeographic regions that so far seemed unsuitable. Archaias angulatus and Calcarina spp. also show an increase in habitat suitability within their native occurrence ranges, suggesting that their tolerance for maximum temperatures has yet not been fully exploited and that they benefit from ocean warming. Our findings suggest an increased role of larger foraminifera as carbonate producers and reef framework builders in future oceans.

Cyanobacterial Diversity and a New Acaryochloris-Like Symbiont from Bahamian Sea-Squirts

Symbiotic interactions between ascidians (sea-squirts) and microbes are poorly understood. Here we characterized the cyanobacteria in the tissues of 8 distinct didemnid taxa from shallow-water marine habitats in the Bahamas Islands by sequencing a fragment of the cyanobacterial 16S rRNA gene and the entire 16S–23S rRNA internal transcribed spacer region (ITS) and by examining symbiont morphology with transmission electron (TEM) and confocal microscopy (CM). As described previously for other species, Trididemnum spp. mostly contained symbionts associated with the Prochloron-Synechocystis group. However, sequence analysis of the symbionts in Lissoclinum revealed two unique clades. The first contained a novel cyanobacterial clade, while the second clade was closely associated with Acaryochloris marina. CM revealed the presence of chlorophyll d (chl d) and phycobiliproteins (PBPs) within these symbiont cells, as is characteristic of Acaryochloris species. The presence of symbionts was also observed by TEM inside the tunic of both the adult and larvae of L. fragile, indicating vertical transmission to progeny. Based on molecular phylogenetic and microscopic analyses, Candidatus Acaryochloris bahamiensis nov. sp. is proposed for this symbiotic cyanobacterium. Our results support the hypothesis that photosymbiont communities in ascidians are structured by host phylogeny, but in some cases, also by sampling location.

Phylogeography of the olive sea snake, Aipysurus laevis (Hydrophiinae) indicates Pleistocene range expansion around northern Australia but low contemporary gene flow

Pleistocene sea-level fluctuations profoundly changed landmass configurations around northern Australia. The cyclic emergence of the Torres Strait land bridge and concomitant shifts in the distribution of shallow-water marine habitats repeatedly sundered east and west coast populations. These biogeographical perturbations invoke three possible scenarios regarding the directions of interglacial range expansion: west to east, east to west, or bidirectional. We evaluated these scenarios for the olive sea snake, Aipysurus laevis, by exploring its genetic structure around northern Australia based on 354 individuals from 14 locations in three regions (Western Australia, WA; Gulf of Carpentaria, GoC; Great Barrier Reef, GBR). A 726-bp fragment of the mitochondrial DNA ND4 region revealed 41 variable sites and 38 haplotypes, with no shared haplotypes among the three regions. Population genetic structure was strong overall, phiST=0.78, P<0.001, and coalescent analyses revealed no migration between regions. Genetic diversity was low in the GBR and GoC and the genetic signatures of these regions indicated range or population expansions consistent with their recent marine transgressions around 7000 years ago. By contrast, genetic diversity on most WA reefs was higher and there were no signals of recent expansion events on these reefs. Phylogenetic analyses indicated that GBR and GoC haplotypes were derived from WA haplotypes; however, statistical parsimony suggested that recent range expansion in the GBR-GoC probably occurred from east coast populations, possibly in the Coral Sea. Levels of contemporary female-mediated gene flow varied within regions and reflected potential connectivity among populations afforded by the different regional habitat types.

Records of and Observations on Tanaidaceans (Peracarida) from Shallow Waters of the Caribbean Coast of Mexico

[As in other tropical areas, the tanaidacean fauna of the western Caribbean Sea remains poorly known. Our study is based on the examination of several families of Tanaidacea from samples collected at 30 sites in a variety of shallow-water marine habitats along the Mexican Caribbean coast, located on the westernmost section of the Caribbean Basin. Up to 13 species belonging to seven families and 11 genera were identified. Of these species, four have been previously recorded from the Caribbean coast of Mexico and nine constitute new regional records. Nine species have been known to occur in the Caribbean Basin and four species, Hexapleomera robusta (Moore), Leptochelia dubia (Kroyer), Sinelobus stanfordi (Richardson), and Zeuxo kurilensis (Kussakin & Tzareva) are widely distributed forms, occurring in two or more oceans. Taxonomic and comparative comments are provided for some species recorded in the surveyed area. The male of Pseudotanais (Akanthinotanais) mortenseni Sieg is recognized and documented for the first time, based on the only specimen found., As in other tropical areas, the tanaidacean fauna of the western Caribbean Sea remains poorly known. Our study is based on the examination of several families of Tanaidacea from samples collected at 30 sites in a variety of shallow-water marine habitats along the Mexican Caribbean coast, located on the westernmost section of the Caribbean Basin. Up to 13 species belonging to seven families and 11 genera were identified. Of these species, four have been previously recorded from the Caribbean coast of Mexico and nine constitute new regional records. Nine species have been known to occur in the Caribbean Basin and four species, Hexapleomera robusta (Moore), Leptochelia dubia (Kroyer), Sinelobus stanfordi (Richardson), and Zeuxo kurilensis (Kussakin & Tzareva) are widely distributed forms, occurring in two or more oceans. Taxonomic and comparative comments are provided for some species recorded in the surveyed area. The male of Pseudotanais (Akanthinotanais) mortenseni Sieg is recognized and documented for the first time, based on the only specimen found.]

Nursery-area function of maerl grounds for juvenile queen scallops Aequipecten opercularis and other invertebrates

The services provided by coastal ecosystems such as mangrove forests and sea-grass beds are becoming increasingly recognised, yet the functional role of maerl beds has not been ad- dressed. Maerl forms highly biodiverse habitats composed of loose-lying coralline red algae which build up over thousands of years. These carbonate-rich deposits occur in photic areas with strong water movement; they have a widespread global distribution yet remain one of the most overlooked shallow-water marine habitats, with little known about the ecosystem services maerl may provide. Our diving research in Scotland has shown that pristine live maerl (PLM) grounds fulfil nursery area prerequisites for commercial populations of queen scallops Aequipecten opercularis and other inver- tebrates, such as the soft clam Mya arenaria, the sea urchins Psammechinus miliaris and Echinus escu- lentus, and the starfish Asterias rubens, more effectively than impacted dead maerl and other common substrata. The complex architecture of maerl beds attracts high densities of these juvenile inverte- brates, which use PLM grounds as nursery areas in preference to adjacent substrata. Considering its global distribution, it is highly likely that ecosystem services provided by maerl are considerable. Maerl is easily damaged and killed by a variety of human activities, yet its protection would maintain vital nursery area function, benefiting commercial fishery yields and, pivotally, regional biodiversity.

Our shifting perspectives on the oceans

In the last 15 years new research findings have radically reshaped our understanding of human effects on ocean ecosystems. Here I describe five major shifts in perspective that reveal our impacts to be more severe and persistent than previously appreciated. Firstly, scientists have delved deep into the past and found that the global expansion of European nations across the planet caused the large-scale loss of marine megafauna. In the past century, expansion of industrial scale fishing has continued the process, massively reducing the biomass of exploited species. Secondly, once depleted we are finding that populations rarely rebound rapidly, contrary to a widespread belief in greater resilience of marine compared to terrestrial species. Thirdly, marine ecosystems are being shifted into alternative states that are less desirable from the human perspective and may be stable. It could be difficult, or impossible in some cases, to reverse impacts once inflicted. Fourthly, marine species are at risk of extinction. Loss of shallow water marine habitats is proceeding as rapidly as on land, many species have small geographic ranges, and many possess life history characteristics that leave them highly susceptible to overexploitation. Finally, the deep sea is not beyond harm. Depletion of shallow water fisheries and technological advances are opening up the deep to exploitation and its collateral impacts. If we are to reverse these negative trends we must establish large-scale networks of marine reserves that are off limits to damaging activities and fishing. Such reserves would protect biodiversity, and recover and sustain the world's fisheries productivity.

Organism response to habitat patchiness: species and habitat-dependent recruitment of decapod crustaceans

Habitat fragmentation from natural or anthropogenic causes is a common phenomenon in shallow water marine habitats such as seagrass beds and oyster reefs throughout the world. Thus, habitat- and scale-dependent information on how organisms perceive and respond to changes in the landscape is critical to efforts aimed at predicting the effects of habitat change on population abundance. In estuarine systems, seagrass is considered one of the predominant nursery habitats for numerous ecologically and commercially important species; however, recent information suggests that alternative habitats such as oyster reefs may also be important sites for settlement and refuge. We used artificial seagrass- and shell-filled plastic trays placed on unstructured seafloor in Back Sound, North Carolina, USA to examine the interactive effects of Experiment, Patch size and Habitat type upon recruitment success of four species of decapod crustaceans: the grass shrimps, Palaemonetes intermedius Holthuis, P. pugio Holthuis and P. vulgaris (Say), and the blue crab, Callinectes sapidus Rathbun. Regardless of habitat type, all species of grass shrimp and J1 blue crab responded to habitat patchiness at scales as small as 0.25 to 4 m −2, whereas larger J2–J4 blue crab did not. Mean densities of all three species of grass shrimp responded in a similar manner to patch size, with significantly higher densities in the smallest patch size (0.25 m −2) compared to larger patches (0.5 to 4 m −2). Conversely, mean densities of J1 blue crabs were significantly higher in the largest patch size (4 m −2) compared to smaller patches (0.25 to 1 m −2). There was a negative and significant relationship between the density of grass shrimp predators and density of J1 prey, and no relationship between potential fish predators and J1–J4 prey. Thus, patterns observed for J1 may be dependent upon predators and not habitat patch size. Both species demonstrated different responses to habitat type depending upon relative densities and body size. Mean densities of P. intermedius and P. vulgaris were higher in seagrass than oyster shell during Experiment 1 (May) when shrimp were relatively abundant, but did not differ between habitat types during Experiment 2 (October), when densities were reduced 10-fold. Conversely, densities of P. pugio did not differ between seagrass and oyster shell. Mean densities of J1 blue crab were similar between seagrass and oyster shell, but higher in seagrass than oyster shell for later juvenile stages (J2–J4). Thus, blue crabs may rely equally on seagrass and oyster reefs as an initial settlement and refuge habitat for early juveniles. Our study demonstrates that an organism's response to habitat patchiness is species-specific, and that for a given species, the response is further modified by animal density and body size. The patterns observed in this study further highlight the importance of scale-dependent responses by mobile organisms to complex benthic habitats.

Microphytobenthos: The Ecological Role of the "Secret Garden" of Unvegetated, Shallow-Water Marine Habitats. II. Role in Sediment Stability and Shallow-Water Food Webs

The microphytobenthos form an important component of all shallow-water ecosystems where enough light reaches the sediment surface to support appreciable primary production. Although less conspicuous than macroalgae or vascular plants, the microphytobenthos can contribute significantly to primary production and can modify habitat characteristics. The microphytobenthos alter sediment properties (e.g., erodibility) both directly, in the extreme forming a mat or scum on the sediment surface, and indirectly by modifying the activities of benthic infauna (e.g., pelletization, burrowing, tube building, and sediment tracking). Carbon dioxide fixed by the microphytobenthos supports higher, grazing trophic levels. These include deposit-feeding and suspension-feeding macrofauna as well as meiofauna and microfauna. Quantitative relations between the feeding and growth rates of macrofauna and the abundance of microphytobenthos and suspended organic matter (i.e., functional responses) are reviewed. Given the current state of knowledge of the direct and indirect interactions involving trophic dynamics, sediment properties, and benthic microalgae, we argue for reductionist studies of particular interactions as distinct entities. This is a prerequisite for the emergence of a comprehensive picture of unvegetated ecosystems and the ability to predict their responses to man’s activities. *** DIRECT SUPPORT *** A01BY074 00005

Toward New Paradigms in Coastal Resource Management: Linkages and Institutional Effectiveness

Explosive population growth is expected to continue in coastal regions, and growth rates many times the national average are expected in many coastal counties in the next two decades. Most shallow-water marine habitats now exhibit “stress” from human activities and linkages between adverse environmental impacts and coastal development are apparent. These linkages are complex, often not well understood, yet are expected to increase in strength as coastal populations expand. Sound science-based management strategies are essential if we are to preclude continued deterioration of coastal environments. Environmental management is a politically mediated activity, however, and a broad array of organizations, both public and private, collectively determine societal response to management decisions. While our current regulatory infrastructure has an examplary record of achievement in environmental protection, the fact remains that adverse impacts to shallow-water marine habitats continue at significant rates. Both lack of scientific information and structural problems in our current institutional infrastructure are identified as impediments to better management performance for coastal habitats. Seven structural impediments to efficient science-based management in our current institutional infrastructure are identified. The issues are complex and comprehensive reform is politically difficult. Nonetheless, the magnitude, geographic scale, and temporal urgency of anticipated impacts from future growth and development scenarios argues strongly for the implementation of sound practical solutions to environmental protection on a sustained basis. Factors affecting management performance will also be amplified in an environment of limited investment in research and management infrastructure. Among the central themes are that science-based management practices in the future will require holistic approaches in which environment and economic development are inseparable. To work effectively large-scale, regional management schemes must build political consensus and integrate knowledge at unprecedented rates. Processes that increase rates of dissemination of scientific information into the public policy arena can significantly enhance management performance. Serious doubts are raised as to whether the current regulatory infrastructure can adequately respond to the complexicty, scale, and urgency future coastal management will demand. While comprehensive institutional reform will be difficult, a number of ideas are advanced in the context of improving institutional performance to a level necessary for large-scale, sustained management of coastal ecosystems.

Microphytobenthos: The Ecological Role of the "Secret Garden" of Unvegetated, Shallow-Water Marine Habitats. I. Distribution, Abundance and Primary Production

The microphytobenthos consists of unicellular eukaryotic algae and cyanobacteria that grow within the upper several millimeters of illuminated sediments, typically appearing only as a subtle brownish or greenish shading. The surficial layer of the sediment is a zone of intense microbial and geochemical activity and of considerable physical reworking. In many shallow ecosystems, the biomass of benthic microalgae often exceeds that of the phytoplankton in the overlying waters. Direct comparison of the abundance of benthic and suspended microalgae is complicated by the means used to measure biomass and by the vertical and horizontal distribution of the microphytobenthos in the sediment. Where biomass has been estimated as chlorophyll a, there may be negligible to large (40%) error due to interference by degradation products, except where chlorophyll is measured by high-performance liquid chromatography. The vertical distribution of microphytobenthos, aside from mat-forming species, is determined by the opposing effects of their vertical migration, which tends to concentrate them near the surface, and physical mixing by overlying currents, which tends to cause an even vertical distribution through the mixed layer of sediment. Uncertainties in vertical distribution are compounded by frequently patchy horizontal distribution. Under-sampling on small (<1 m) scales can lead to errors in the estimate that are comparable to the ranges of seasonal and geographic variation. These uncertainties are compounded by biases in the techniques used to estimate production by the microphytobenthos. In most environments studied, biomass (as chlorophyll a) and light availability appear to be the principal determinants of benthic primary production. The effect of variable light intensities on integral production can be described by a functional response curve. When normalized to the chlorophyll content of the surficial sediment, the residual variation in the data described by the functional response curve is due to changes in the chlorophyll-specific response to irradiance. Production by the benthos is often a significant fraction of production in the water column and microphytobenthos may contribute directly to water column production when they are resuspended. Thus on both the basis of biomass and biogeochemical reactivity, benthic microalgae play significant roles in system productivity and trophic dynamics, as well as such habitat characteristics as sediment stability. *** DIRECT SUPPORT *** A01BY074 00003