Intertidal Habitats Research Articles

Review and guide to the isopods (Crustacea, Isopoda) of littoral and sublittoral marine habitats in the Southern California Bight.

The isopod crustaceans reported from or expected to occur in littoral and sublittoral marine habitats of the Southern California Bight (SCB) in the northeastern Pacific Ocean are reviewed. A total of 190 species, representing 105 genera in 42 families and six suborders are covered. Approximately 84% of these isopods represent described species with the remaining 16% comprising well-documented "provisional" but undescribed species. Cymothoida and Asellota are the most diverse of the six suborders, accounting for ca. 36% and 29% of the species, respectively. Valvifera and Sphaeromatidea are the next most speciose suborders with between 13-15% of the species each, while the suborder Limnorioidea represents fewer than 2% of the SCB isopod fauna. Finally, the mostly terrestrial suborder Oniscidea accounts for ca. 5% of the species treated herein, each which occurs at or above the high tide mark in intertidal habitats. A key to the suborders and superfamilies is presented followed by nine keys to the SCB species within each of the resultant groups. Figures are provided for most species. Bathymetric range, geographic distribution, type locality, habitat, body size, and a comprehensive list of references are included for most species.

Chloroplast genome analysis of three Acanthus species reveal the adaptation of mangrove to intertidal habitats

Acanthus is a distinctive genus that covers three species with different ecological niches including Acanthus mollis (arid terrestrial), Acanthus leucostachyus (damp forest) and Acanthus ilicifolius (coastal intertidal). It is an intriguing question how these species evolved from terrestrial to coastal intertidal. In the present study, we assembled chloroplast genomes of A. ilicifolius, A. leucostachyus and A. mollis, which exhibited typical quadripartite structures. The sizes were 150,758, 154,686 and 150,339 bp that comprised a large single copy (LSC, 82,963, 86,461 and 82,612 bp), a small single copy (SSC, 17,191, 17,511 and 17,019 bp), and a pair of inverted repeats (IRs, 25,302, 25,357 and 25,354 bp), respectively. Gene annotation revealed that A. ilicifolius, A. leucostachyus and A. mollis contained 113, 112 and 108 unique genes, each of which contained 79, 79 and 74 protein-coding genes, 30, 29 and 30 tRNAs, and 4 rRNA genes, respectively. Differential gene analysis revealed plenty of ndhs gene deletions in the terrestrial plant A. mollis. Nucleotide diversity analysis showed that the psbK, ycf1, ndhG, and rpl22 have the highest nucleotide variability. Compared to A. leucostachyus and A. mollis, seven genes in A. ilicifolius underwent positive selection. Among them, the atpF gene showed a strong positive selection throughout terrestrial to marine evolution and was important for adaptation to coastal intertidal habitats. Phylogenetic analysis indicated that A. ilicifolius has a closer genetic relationship with A. leucostachyus than A. mollis which further confirmed the evolutionary direction of Acanthus going from terrestrial to coastal intertidal zones.

A comparative study on CNN-based semantic segmentation of intertidal mussel beds

Mussels are globally distributed and abundant species on intertidal habitats such as rocky shores where they form dense beds and provide a variety of ecosystem services. The ability to measure mussel abundance on shores with high efficiency and accuracy will enhance assessment of their facilitative services to intertidal ecosystems. Traditional sampling methods, however, are labour intensive and consequently limited in spatial and temporal coverage. To advance such monitoring and quantification processes, four state-of-the-art convolutional neural networks (CNN); namely U-Net, FastSCNN, DeepLab v3+, and HRNet, were compared in their performance to segment mussels at the pixel level either with or without Cityscapes pre-trained weights. All proposed CNN were trained on a photographic dataset of 1455 images generated from field images of mussel beds. CNN trained with the Cityscapes pre-trained weights showed an overall increased model performance as illustrated by mean intersection-over-union (mIoU), loss, overall accuracy (oAcc), and Cohen's kappa coefficient. DeepLab v3+ and HRNet with the combination of Cityscapes pre-trained weights achieved over 95% mIoU and 97% oAcc for assessing distribution and abundance of these important intertidal species. Such combination of approaches is, therefore, recommended for ecologists who wish to conduct image-driven surveys of intertidal ecosystems and the code for this study is available at: https://github.com/Vicellken/CNN-SS-mussel.

Drivers of variability in Blue Carbon stocks and burial rates across European estuarine habitats

The implementation of climate change mitigation strategies based on the conservation and restoration of Blue Carbon ecosystems requires a deep understanding of the magnitude and variability in organic carbon (Corg) storage across and within these ecosystems. This study explored the variability in soil Corg stocks and burial rates across and within intertidal estuarine habitats of the Atlantic European coast and its relation to biotic and abiotic drivers. A total of 136 soil cores were collected across saltmarshes located at different tidal zones (high marsh, N = 45; low marsh, N = 30), seagrass meadows (N = 17) and tidal flats (N = 44), and from the inner to the outer sections of five estuaries characterized by different basin land uses. Soil Corg stocks were higher in high-marsh communities (65 ± 3 Mg ha−1) than in low-marsh communities (38 ± 3 Mg ha−1), seagrass meadows (40 ± 5 Mg ha−1) and unvegetated tidal flats (46 ± 3 Mg ha−1) whereas Corg burial rates also tended to be higher in high marshes (62 ± 13 g m−2 y−1) compared to low marshes (43 ± 15 g m−2 y−1) and tidal flats (35 ± 9 g m−2 y−1). Soil Corg stocks and burial rates decreased from inner to outer estuarine sections in most estuaries reflecting the decrease in the river influence towards the estuary mouth. Higher soil Corg stocks were related to higher content of silt and clay and higher proportion of forest and natural land within the river basin, pointing at new opportunities for protecting coastal natural carbon sinks based on the conservation and restoration of upland ecosystems. Our study contributes to the global inventory of Blue Carbon by adding data from unexplored regions and habitats in Europe, and by identifying drivers of variability across and within estuaries.

Unraveling molecular mechanisms underlying low-temperature adaptation in Laguncularia racemosa

Laguncularia racemosa (L.) C.F. Gaertn is a controversial species in China, in terms of being a pioneer species for mangrove restoration and a putative invasive species occupying natural habitats. The tolerance to chilling stress allows L. racemosa to adapt to extreme climate change. However, little is known about the molecular-level chilling resistance mechanisms in L. racemosa, which restricts our understanding of its biological features and invasion potential. In this study, L. racemosa seedlings were treated with freezing temperature (0 °C) at four durations (0 h, 3 h, 12 h and 24 h of recovery after treatment), and both physiological and transcriptional regulations underlying chilling stress resistance were investigated. Chilling stress caused damage to the cell membrane system and reduced photosynthesis efficiency of L. racemosa seedlings. To combat the adverse impacts, plasma membrane biosynthesis and antioxidant processes were substantially enhanced. After 24 h of recovery, the seedlings nearly recovered to normal growth condition, except for the processes related to photosynthesis, indicating their vigorous adaptation to short-term chilling stress. Importantly, the individuals from higher latitude displayed better adaptation to chilling injury than those from lower latitude, highlighting the role of long-term heredity × environment interactions in promoting the chilling resistance capacity of L. racemosa. These features allow L. racemosa to survive in extremely cold weather, but may also increase its risk of invasion into intertidal ecosystems. Together, our findings present a comprehensive view of the chilling-adaptative mechanisms of L. racemosa, which provide clues for better evaluating the invasive potential of L. racemosa.

Acclimation in intertidal animals reduces potential pathogen load and increases survival following a heatwave

Intertidal animals can experience intense heat during a heatwave, leading to mortality. The causes of death for intertidal animals following heatwaves have often been attributed to a breakdown in physiological processes. This, however, contrasts with research in other animals where heatwave mortality is attributed to existing or opportunistic diseases. We acclimated intertidal oysters to four treatment levels, including an antibiotic treatment, and then exposed all treatments to a 50°C heatwave for 2h, replicating what can be experienced on Australian shorelines. We found that both acclimation and antibiotics increased survival and reduced the presence of potential pathogens. Non-acclimated oysters had a significant shift in their microbiome, with increasing abundances of bacteria from the Vibrio genera, including known potential pathogens. Our results demonstrate that bacterial infection plays a pivotal role in post-heatwave mortality. We anticipate these findings to inform the management of aquaculture and intertidal habitats as climate change intensifies.

A Small-scale Wave Tank For Living Shoreline Extension And Outreach

Hardened structures, such as bulkheads and seawalls, are currently the primary choice of shoreline protection for waterfront property owners. However, hardened shorelines are known to enhance erosion and often promote the loss of intertidal habitat. Living shorelines are a collection of environmentally friendly construction techniques that serve as an alternative to hardened shorelines through the incorporation of natural materials, such as native plants. To enhance extension and outreach efforts related to the promotion of living shorelines, we created a small-scale, hands-on wave tank that demonstrates the benefits of natural and living shorelines relative to hardened structures. This interactive tool allows the audience to view the differences between natural, living, and hardened shorelines for both aesthetics and wave energy reduction.

KEANEKARAGAMAN KELAS BIVALVIA DI PANTAI CIBUAYA UJUNG GENTENG

Cibuaya Beach is one of the beaches in Ujung Genteng Village that is used as a tourist destination because the beach is still very clean and natural. Cibuaya Beach has large beach sand grains and is dominated by mollusk shell fragments. The intertidal zone is the zone bounded by the tidal line and is the narrowest of the marine zones. The coastal ecosystem of Cibuaya Beach consists of coral reefs, seagrasses, and coastal vegetation. This study aims to determine the diversity of Bivalves in Cibuaya Beach Ujung Genteng. This research was conducted at Cibuaya Beach Ujung Genteng in March-April 2022. Determination of the research location using the belt transect method by purposive sampling at three stations namely rocky sand (station 1), seagrass (station 2), and coral reef (station 3). The results obtained were 148 individuals with 11 Bivalve species comprising six families. The value of the diversity index (H') ranged from 1.58-1.99 classified as medium. The value of the evenness index (E) ranges from 0.83-0.88 classified as high. The dominance index value (D) ranges from 0.18-0.24 which is low. The measurement results of abiotic parameters, namely temperature, pH, salinity, humidity, current speed, and light intensity show good values for marine bivalve life. Therefore, the Cibuaya Beach intertidal ecosystem is suitable for the life of the Bivalve class.

The impact of marine heatwaves on rocky intertidal communities: evidence of accumulative carryover effects of marine heatwaves

The frequency and duration of marine heat waves (MHWs) have recently increased. There is therefore an urgent need to understand the response of marine organisms to MHWs. However, most estimates of MHW impacts on abundances include the effects of environmental stochasticity other than the MHWs. In addition, although MHWs sometimes persist for year-round or occur repeatedly for shorter periods, the accumulative carryover effects (ACEs)— the effects of sequential events accumulating additively over time— of MHWs on organisms have never been evaluated. Furthermore, the relationship between species niche traits other than thermal niches and susceptibility to MHWs is unknown. We examined the impacts of MHWs in southeastern Hokkaido, northern Japan, in summer from 2010 to 2016 on rocky intertidal communities by distinguishing MHW effects from environmental stochasticity. We asked (1) Did MHWs have ACEs on four major functional groups: macroalgae, sessile invertebrates, herbivorous invertebrates, and carnivorous invertebrates? (2) Does ignoring ACEs lead to biased assessments? (3) How did the effects of the MHWs on functional groups and their subsequent recovery differ? And (4) How does the susceptibility to MHWs differ with species niche (thermal and vertical) traits? We detected ACEs of MHWs and found that if they are ignored, the effects of MHWs can be underestimated. Although MHWs are known to reduce the abundance of macroalgae and increase that of sessile invertebrates in rocky intertidal habitats, our results show that macroalgal abundance increased during and after MHWs, whereas sessile invertebrates showed no change during or after MHWs. The abundance of herbivorous mollusks decreased during and after MHWs. Carnivorous invertebrates declined during MHWs and in the first year after MHWs. During and after MHWs, abundances of species with low thermal niches decreased and those with high thermal niches increased. There were no differences in response to MHWs between vertical niches when accumulative carryover effects were ignored. These results emphasize the importance of considering ACEs when assessing the response of marine organisms to MHWs, and that more studies of these responses are needed for a variety of ecosystems, regions and organisms to predict the responses of marine organisms.

A spatial explicit vulnerability assessment for a coastal socio-ecological Natura 2000 site

In line with the global trend, the Ria de Aveiro coastal lagoon is subjected to multiple co-occurring pressures threatening vital benefits flowing from nature to people. The main objective of this research was to assess the status of habitats important for ecosystem services in the Ria de Aveiro by identifying vulnerable areas to anthropogenic threats. The pressures from seven relevant human activities (recreation, services, aquaculture, agriculture, commercial development, unintended impacts from management, and invasive alien species) were analysed based on their spatiotemporal distribution (exposure) and impact over the EUNIS habitats (EUNIS codes A2.2, A2.22 – sand flats and beaches; A2.3 – mud flats; A2.61 – seagrasses; A2.5, A2.53C, A2.535, A2.545, A2.554 – salt marshes; and, X10 – ‘Bocage,’ a landscape of small-hedged fields) in seven distinct landscape units. A prospective scenario, co-developed for the year 2030, was evaluated using a map-based risk assessment tool and brought forward the near-term vulnerability of the seagrass biotope. The highest risks posed to intertidal habitats (mud flats and salt marshes) were driven mainly by environmental management activities that support critical socio-economic sectors. Our methodology evaluated plausible threats to habitats in the near term, established baseline knowledge for the adaptive management process in Ria de Aveiro Natura 2000 site, and showcased how future assessments can inform the operationalization of ecosystem-based management as new information becomes available.

Going under: The implications of sea‐level rise and reduced light availability on intertidal primary production

AbstractEstuarine intertidal flats are known for high rates of primary production, however, globally these ecosystems are under threat from rising sea‐level and accelerated inputs of terrestrial sediments. These stressors simultaneously alter the duration of submersion/emersion periods and water‐column turbidity impacting seafloor photoperiods. To assess how changes in submergence time and water‐clarity can affect benthic primary production, we derived in situ seasonal photosynthesis‐irradiance (P‐I) curves over 2 yr. These were conducted during submerged and emerged periods in a seagrass meadow (Zostera muelleri) and an unvegetated sandflat (dominated by microphytobenthos). P‐I curves showed strong light responses during submergence in both habitats and seagrass during emergence, but in the exposed sandflat there was little relationship between light availability and photosynthesis. Light‐saturated measures of gross primary production (GPPsat) were 2.1 (submerged) and 4.1 times (emerged) higher in the seagrass than the sandflat habitat. Submerged GPPsat was always higher than emerged GPPsat, but this difference was much more pronounced in the sandflat habitat (2.4 vs. 1.3 times for seagrass). Integrating seasonally averaged P‐I curves for both tidal states into a simple model suggests that increasing submergence time could increase primary production in both habitats. However, reductions in water‐clarity will decrease submerged primary production; an effect that will be exacerbated with sea‐level rise. The sandflat trophic state was more sensitive to these environmental stressors because emerged production could not compensate for reductions during submergence. Collectively, regional management of water‐clarity may be key to providing resilience to intertidal habitats, against the inevitable effects of sea‐level rise.

Lethal and sublethal implications of low temperature exposure for three intertidal predators

Benthic invertebrate predators play a key role in top-down trophic regulation in intertidal ecosystems. While the physiological and ecological consequences of predator exposure to high temperatures during summer low tides are increasingly well-studied, the effects of cold exposure during winter low tides remain poorly understood. To address this knowledge gap, we measured the supercooling points, survival, and feeding rates of three intertidal predator species in British Columbia, Canada — the sea stars Pisaster ochraceus and Evasterias troschelii and the dogwhelk Nucella lamellosa — in response to exposure to sub-zero air temperatures. Overall, we found that all three predators exhibited evidence of internal freezing at relatively mild sub-zero temperatures, with sea stars exhibiting an average supercooling point of −2.50 °C, and the dogwhelk averaging approximately −3.99 °C. None of the tested species are strongly freeze tolerant, as evidenced by moderate-to-low survival rates after exposure to −8 °C air. All three predators exhibited significantly reduced feeding rates over a two-week period following a single 3-h sublethal (−0.5 °C) exposure event. We also quantified variation in predator body temperature among thermal microhabitats during winter low tides. Predators that were found at the base of large boulders, on the sediment, and within crevices had higher body temperatures during winter low tides, as compared to those situated in other microhabitats. However, we did not find evidence of behavioural thermoregulation via selective microhabitat use during cold weather. Since these intertidal predators are less freeze tolerant than their preferred prey, winter low temperature exposures can have important implications for organism survival and predator-prey dynamics across thermal gradients at both local (habitat-driven) and geographic (climate-driven) scales.

Long‐term coastal macrobenthic Community Trajectory Analysis reveals habitat‐dependent stability patterns

Long‐term monitoring programs are fundamental to detect changes in ecosystem health and understand ecological processes. In the current context of increasing anthropogenic threats on marine ecosystems, understanding the dynamics and response of communities becomes essential. We used data collected over 14 years in the REBENT benthic coastal invertebrates monitoring program, at a regional scale in the North‐East Atlantic, covering a total of 26 sites and 979 taxa. Four distinct habitats were studied: two biogenic habitats associated with foundation species in the intertidal and subtidal zones and two bare sedimentary habitats in the same respective tidal zones. We used community trajectory analysis (CTA), a statistical approach that allows for quantitative measures and comparisons of temporal trajectories of ecosystems. We compared observed community trajectories to trajectories simulated under a non‐directional null model in order to better understand the dynamics of the communities, their potential drivers, and the role of the studied habitats in these dynamics. Despite strong differences in the community compositions between sites and habitats, the communities followed non‐directional dynamics during the 14 years monitored, which suggested stability at the regional scale. However, the shape, size, and direction of the trajectories of benthic communities were more similar within than among habitats, also suggesting the influence of the nature of the habitat on community dynamics. Results showed a higher variability in community composition the first years of the monitoring in the intertidal bare habitat and confirmed the role of biogenic habitats in maintaining temporal stability. They also highlighted the need to apprehend the role of transient and rare species and the scale of observation in temporal beta diversity analyses. Finally, our study confirmed the usefulness of CTA to link observed trajectory patterns to fundamental ecological processes.

Structuring algae as buffers for heavy metals and trace elements in the Canary Islands intertidal habitat

Coastal marine pollution from sewage pipes, waste discharges, can seriously affect intertidal organisms. Therefore, the aim of this study is to know if the structuring algae in the Canary intertidal can act as buffers against pollution. Samples were taken in the island of Tenerife (Canary Islands, Spain) from the intertidal water of Anemonia sulcata (anemone), Palaemon elegans (shrimp), Gongolaria abies-marina and Jania virgata (both structuring algae). Each sample was analyzed by Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) obtaining values for metals and trace elements (Al, Cd, Pb, Ca, K, Mg, Na, B, Ba, Ba, Co, Cr, Cu, Fe, Li, Mn, Mo, Ni, Sr, V and Zn). Higher concentrations were obtained in the two structuring algal species, with J. vigata having higher concentrations than G. abies-marina. Specimens of A. sulcata showed higher concentrations of trace elements and heavy metals than P. elegans. P. elegans y A. sulcata showed higher heavy metal concentrations and trace elements when algae were not present in the pool. Algae have a great buffering role in the intertidal of the Canary Islands.

A pioneer morphological and genetic study of the intertidal fauna of the Gerlache Strait (Antarctic Peninsula).

The underexplored intertidal ecosystems of Antarctica are facing rapid changes in important environmental factors. Associated with temperature increase, reduction in coastal ice will soon expose new ice-free areas that will be colonized by local or distant biota. To enable detection of future changes in faunal composition, a biodiversity baseline is urgently required. Here, we evaluated intertidal faunal diversity at 13 locations around the Gerlache Strait (western Antarctic Peninsula), using a combination of a quadrat approach, morphological identification and genetic characterization. Our data highlight a community structure comprising four generally distributed and highly abundant species (the flatworm Obrimoposthia wandeli, the bivalve Kidderia subquadrata, and the gastropods Laevilitorina umbilicata and Laevilitorina caliginosa) as well as 79 rarer and less widely encountered species. The most abundant species thrive in the intertidal zone due to their ability to either survive overwinter in situ or to rapidly colonize this zone when conditions allow. In addition, we confirmed the presence of multiple trophic levels at nearly all locations, suggesting that complex inter-specific interactions occur within these communities. Diversity indices contrasted between sampling locations (from 3 to 32 species) and multivariate approaches identified three main groups. This confirms the importance of environmental heterogeneity in shaping diversity patterns within the investigated area. Finally, we provide the first genetic and photographic baseline of the Antarctic intertidal fauna (106 sequences, 137 macrophotographs), as well as preliminary insights on the biogeography of several species. Taken together, these results provide a timely catalyst to assess the diversity and to inform studies of the potential resilience of these intertidal communities.

The role of the epidermal physode layer in UV protection of Fucus species

Phlorotannins are believed to provide UV protection in brown algae. In Fucus species, phlorotannin-rich vesicles (“physodes”) form an “epidermal physode layer”, which might represent the anatomical structure responsible for UV protection. However, this layer has been neglected so far; instead, phlorotannin contents of entire thalli were studied in UV exposure experiments.We employed fluorometric methods to investigate in which wavelength region and to which degree the epidermal physode layer of two Fucus species reduces the transmittance of UV radiation. For comparison, we also studied Saccharina latissima, a brown algal species without epidermal physode layer.We could show that the epidermal physode layer absorbs throughout the entire UV wavelength range and reduces the epidermal UV-B transmittance into the thallus strongly (15% transmitted in F. vesiculosus vs. 80–100% in S. latissima). UV-B transmittances varied with growth depth and the variations correlated with photosystem II (PSII) stress responses upon artificial UV-B illumination. We found that the UV-B protection is more than sufficient for natural UV-B levels and of rather constitutive nature.In conclusion, the epidermal physode layer appears to be the anatomical feature exerting UV protection by phlorotannins in Fucus species and might thus be a core adaptation that enables Fucales the colonization of the intertidal habitat.

Predicting diversity in benthic macro‐scale communities associated with mussel matrices in three Pacific ecoregions

AbstractMarine mussels are ubiquitous and their tough byssal threads allow for the formation of expansive, age‐aggregated mats known as mussel matrices which can host marine invertebrates and algal macro‐benthic communities playing an important role in food‐web dynamics. Yet, despite the significant implications for biodiversity and intertidal ecosystem functioning, the role of mussel size, individual morphology and community arrangement in determining the structure of the associated community has never been investigated. Species representative of the green, brown and red marine algal phyla as well as polychaetes, crustaceans and gastropods were sampled from mussel matrices in the Guayaquil (GUAY), Humboldtian (HWS, HNS) and North American Pacific Fjordland (NAPF) marine ecoregions. Linear mixed effects modelling (LMM) and linear effects modelling (LEM) were used to determine the effect of mussel matrices as a predictor of species diversity by incorporating variability due to ecoregion and sampling site. Shell length and stratum index demonstrated significant effect on species richness (Sobs) and Menhinick's richness (D), while stratum index demonstrated an effect on species diversity (H). In the linear mixed model analysis, shell length explained most of the variation in Menhinick's richness (D) and observed species richness (Sobs), while stratum index explained most of the variation in (D) in the linear effects model. Our findings reveal that the level of complexity in mussel assemblages plays a major role in determining species diversity.

Production and accumulation of reef framework by calcifying corals and macroalgae on a remote Indian Ocean cay

Abstract. Coral reefs face increasing pressures in response to unprecedented rates of environmental change at present. The coral reef physical framework is formed through the production of calcium carbonate (CaCO3) and maintained by marine organisms, primarily hermatypic corals, and calcifying algae. The northern part of Western Australia, known as the Kimberley, has largely escaped land-based anthropogenic impacts and this study provides important metabolic data on reef-building organisms from an undisturbed set of marine habitats. From the reef platform of Browse Island, located on the mid-shelf just inside the 200 m isobath off the Kimberley coast, specimens of the dominant coral (six species) and algal (five species) taxa were collected and incubated ex situ in light and dark shipboard experimental mesocosms for 4 h to measure rates of calcification and production patterns of oxygen. During experimental light and dark incubations, all algae were net autotrophic producing 6 to 111 mmolO2m-2d-1. In contrast, most corals were net consumers of O2 with average net fluxes ranging from −42 to 47 mmolO2m-2d-1. The net change in pH was generally negative for corals and calcifying algae (−0.01 to −0.08 h−1). Resulting net calcification rates (1.9 to 9.9 gCaCO3m-2d-1) for corals and calcifying algae (Halimeda and Galaxura) were all positive and were strongly correlated with net O2 production. In intertidal habitats around Browse Island, estimated relative contributions of coral and Halimeda to the reef production of CaCO3 were similar at around 600 to 840 gm-2yr-1. The low reef platform had very low coral cover of < 3 % which made a smaller contribution to calcification of ∼ 240 gCaCO3m-2yr-1. Calcification on the subtidal reef slope was predominantly from corals, producing ∼ 1540 gCaCO3m-2yr-1, twice that of Halimeda. These data provide the first measures of community metabolism from the offshore reef systems of the Kimberley. The relative contributions of the main reef builders, in these undisturbed areas, to net community metabolism and CaCO3 production is important to understand exclusively climate-driven negative effects on tropical reefs.

Understanding the role of microhabitats in intertidal rock pools to guide future eco-engineering designs

Intertidal rock pools support diverse assemblages. While there is much research on the importance of rock pools in supporting mobile diversity on rocky shores, there is limited knowledge regarding the role of physical features (microhabitats) within these habitats. Understanding the features of pools that support diversity is crucial to conserve and potentially mimic these important intertidal habitats in restoration projects. Here, we classified and quantified the types of physical features, hereafter “microhabitats” (overhangs and pits), within rock pools at different locations in and around a highly urbanised estuary, Sydney Harbour, Australia. The use of different microhabitats within rock pools by mobile macro-invertebrates was also examined in one location. We surveyed natural rock pools in summer (2 times) and winter (2 times) at seven sites: two sites from each of the inner and outer zones of Sydney Harbour, and three sites along the open coast of Sydney. We found that the type and size of microhabitats within pools decreased from the coastal towards inner harbour sites. Along the open coast, the richness of mobile taxa increased in rock pools with overhangs or pits. Only rock pools with overhangs had increased mobile abundances, likely driven by the gastropod Nerita melanotragus. Several species occurred in greater frequency in pools with overhangs. There was no effect of pits on abundances. This survey suggests that some microhabitats may play an important role in the diversity and abundance of mobile macro-invertebrates in rock pools. A detailed understanding of the local and regional scales of microhabitats should be used to inform eco-engineering of intertidal foreshores.

Sexual Maturity and Macronutrient Contents in Diopatra sp. (Onuphidae, Polychaeta) Maintained at Different Salinity Levels

Diopatra sp. (Onuphidae, Polychaeta) is an economically important polychaete species commonly used as a fishing bait by local anglers in Cilacap, Central Java Province. Some biological aspects of this local species, however, have not been studied yet. The aim of this research was to see the effect of salinity levels on the sexual maturity and the macronutrient contents of the animals. Diopatra specimens in the present study were collected from the intertidal mangrove habitats of Jeruklegi Village, Cilacap, in sexually immature condition. The worms were then transported to the laboratory and were maintained in containers with four different salinity levels, i.e. 10, 15, 20 and 25 ppt over the next two months. The sexual maturity of the animals were observed based on the presence or absence of coelomic gametes. Proximate analysis was performed to determine macronutrient contents of the animals. The effect of salinity levels on the animals' sexual maturity and macronutrient contents was analyzed using one-way ANOVA. The results showed that salinity levels did not significantly affect the sexual maturity level of Diopatra worms (p > 0.05). Similarly, they did not affect the protein and fat contents, but impacted the carbohydrate content of the animals (p < 0.05). The protein and the fat contents in Diopatra sp., i.e. 41–43% and 6–9%, respectively, met the amount required to be used as shrimp broodstock and fish feeds. While the species has the potential for use in local aquaculture, the annual reproductive cycle as well as the identity of the species, however, require further research.