Subtidal Regions Research Articles

Opheliidae (Annelida: Polychaeta) from the western Pacific islands, including five new species

Intertidal, shallow subtidal and deep-water opheliids from the Hawaiian Islands, Guam in the Mariana Islands and Tutuila in American Samoa were examined and nine species are described, five of which are new. Armandia garretti sp. nov. and A. circumpapillata sp. nov. are new species proposed for previous records of A. intermedia Fauvel, 1902 from Hawaii. Armandia cf. paraintermedia Parapar Moreira, 2015 is recorded from intertidal muddy bottoms of Tutuila and A. amakusaesis Saito, Tamaki Imajima, 2000 from subtidal regions in Guam. Polyophthalmus mauliola sp. nov. is described from Hawaiian material and a comparative table with relevant morphological features of eight species of this genus is presented. Ophelina cf. chaetifera (Hartman, 1965) and Ophelina abranchiata Stop-Bowitz, 1948 are new records to Hawaii from up to 507 m depth, Ophelina kohni sp. nov. is described from shallow waters of Guam and Ophelina manana sp. nov. is described from Mamala Bay, Oahu.

ALGAE AND DIETARY DIETS

Algae involve several species of multicellular and macroscopic marine algae found in the coastal region between high to low tide in the sub-tidal region up to a depth where 0.01 % photosynthetic light is available. Based on their pigmentation, seaweeds were classified in to Chlorophyta (green algae), Phaeophyta (Brown algae) and Rhodophyta (Red algae). Algae are not classified as true plants. They lack an organized vascular system for absorbing nutrients. The root called the holdfast, the stem is the stripe and the leaf of the seaweed is the blade or frond. Like flowering plants, they are able to use chlorophyll to conduct the process of photosynthesis and create their own food for growth.
 In marine ecosystems, macroalgae communities provide nutrition, reproduction, and an accommodating environment for other living organisms. Algae play a vital role in various aspects compared to other aquatic resources. Because of these properties, macroalgae are some of the most important organisms maintaining the ecosystem’s stability. They are also excellent source of bioactive compounds such as carotenoids, dietary fibers, proteins, essential fatty acids, vitamins, minerals and important sources of medicines and fertilizers.
 
 

Movement of pulsed resource subsidies from kelp forests to deep fjords.

Resource subsidies in the form of allochthonous primary production drive secondary production in many ecosystems, often sustaining diversity and overall productivity. Despite their importance in structuring marine communities, there is little understanding of how subsidies move through juxtaposed habitats and into recipient communities. We investigated the transport of detritus from kelp forests to a deep Arctic fjord (northern Norway). We quantified the seasonal abundance and size structure of kelp detritus in shallow subtidal (0‒12m), deep subtidal (12‒85m), and deep fjord (400‒450m) habitats using a combination of camera surveys, dive observations, and detritus collections over 1year. Detritus formed dense accumulations in habitats adjacent to kelp forests, and the timing of depositions coincided with the discrete loss of whole kelp blades during spring. We tracked these blades through the deep subtidal and into the deep fjord, and showed they act as a short-term resource pulse transported over several weeks. In deep subtidal regions, detritus consisted mostly of fragments and its depth distribution was similar across seasons (50% of total observations). Tagged pieces of detritus moved slowly out of kelp forests (displaced 4‒50m (mean 11.8m ± 8.5 SD) in 11‒17days, based on minimum estimates from recovered pieces), and most (75%) variability in the rate of export was related to wave exposure and substrate. Tight resource coupling between kelp forests and deep fjords indicate that changes in kelp abundance would propagate through to deep fjord ecosystems, with likely consequences for the ecosystem functioning and services they provide.

Palmophyllum crassum, a New Record of an Ancient Species in Green Algae from Korea

The continuous exploration in deep seawater from Korea makes us lead the discovery of ancient Chlorophyta, Palmophyllum, in the Korean coast. The phylogenetic analyses of 18S rRNA and rbcL genes demonstrate that our specimens are Palmophyllum crassum (Naccari) Rabenhorst, recorded in Japan and clearly distinguished from P. umbracola from New Zealand and California, USA. Palmophyllum crassum grows in the subtidal region, 8-30 m deep, and has a crustose thallus which is closely adherent to substrates such as non-geniculate crustose coralline algae, sponge, shells, or rocks. P. crassum is composed of numerous spherical cells embedded in the gelatinous matrix. The discovery of this ancient green seaweed implies that the Korean coast is one of the hotspots of algal species diversity and has the suitable marine environment for algal speciation. We suggest the grounds to conserve the Korean coast environmentally as the biodiversity center of marine species by studying the phylogeny of seaweeds.

Defaunation of meiofauna in Mumbai bay (India) - A severely polluted area

Meiofauna plays an important role in the benthic food web of shallow water ecosystems. In the present study, the status of meiofauna was addressed in the intertidal and subtidal environment of Mumbai bay (West coast of India), a severely polluted area. A total of four intertidal sites were sampled monthly for a period of six months (October 2010–March 2011) and eight subtidal sites were sampled thrice (October 2010, December 2010 and March 2011). The results revealed the defaunation of meiofauna occurring in Mumbai bay. Among the intertidal sites, Elephanta was very poor in terms of density and diversity, whereas in the subtidal environment, most of the sites were almost devoid of meiofauna. Compared to an earlier study in the subtidal sediments off Mumbai (Sajan, 2003), meiofaunal density in the present study was almost 40 times less (maximum density 25.5 ind. 10 cm−2). Even, such low densities have never been recorded earlier from any other subtidal regions of the west coast of India from an equivalent depth. Loss of meiofauna is quite alarming as it could alter the biogeochemical cycles of the Mumbai coastal area, thereby affecting the ecosystem functioning.

Seawater‐groundwater mixing in and fluxes from coastal sediment overlying discrete fresh seepage zones: A modeling study

AbstractSubmarine fresh groundwater discharging from discrete zones such as conduits overlain by thick sediment remains poorly documented and understood despite common anecdotal accounts of it. We analyzed this phenomenon by a suite of variable‐density, variably saturated groundwater flow simulations guided by field studies. The field observations included point flux and salinity measurements using seepage meters spread across the intertidal and the subtidal zones. The discretely measured seepage fluxes in the subtidal region were as high and the salinity was as fresh as those from the intertidal zone. Both fluxes and salinities varied with tides. Two‐dimensional simulations of the idealized beach‐ocean vertical section with discrete freshwater springs at the base showed the development of seawater recirculation cells along the edge of freshwater discharge plumes emanating from the outlets, causing mixing. Brackish water discharges at the sediment‐water interface above where the plume mixes with the recirculating seawater. Sensitivity analyses showed that stronger terrestrial fresh groundwater flow increases the freshwater plume size but does not affect the mixing zone width. Tidal oscillations and a dynamic fresh groundwater flow widened the mixing zones and increased pore water flux across the sediment‐water interface. Sediment thickness had a minor effect on the width of both the freshwater plume and its surrounding mixing zone. The subtidal freshwater plume and mixing zone likely represent a unique but potentially ubiquitous setting which hosts dramatic ecological and chemical gradients. Their local biogeochemical niche and coastal scale ecosystem impacts will need to be considered in investigations of coastlines.

Impact of Armored Shorelines on Shore-Zone Fish Density in a Mid-Atlantic, USA, Estuary: Modulation by Hypoxia and Temperature

Anthropogenic modifications of estuarine environments, including shoreline hardening and corresponding alteration of water quality, are accelerating worldwide as human population increases in coastal regions. Estuarine fish species inhabiting temperate ecosystems are adapted to extreme variations in environmental conditions including water temperature, salinity, and dissolved oxygen across seasonal, daily, and hourly time scales. The present research utilized quantitative sampling to examine the spatiotemporal distribution of shore-zone estuarine fish species in association with four unique shoreline types across a range of water temperature and dissolved oxygen conditions. Fish were collected from the intertidal and shallow subtidal region of four shoreline types, Spartina alterniflora marsh, Phragmites australis marsh, riprap, and bulkhead, in the summer and fall of 2009 and 2010. Analyses were performed to (1) compare mean fish density among shoreline types across all water conditions and (2) explore relationships of the complete fish assemblage, three functional species groupings, and two fish species (Fundulus heteroclitus and Menidia menidia) to unique shoreline/water conditions. Significantly greater mean fish densities were found along S. alterniflora shorelines than armored shorelines. Several metrics including fish density, species richness, and occurrence rates suggest S. alterniflora shorelines may serve as a form of refuge habitat during periods of low dissolved oxygen and high temperatures for various species, particularly littoral-demersal species including F. heteroclitus. Potential mechanisms that could contribute to a habitat providing refuge during adverse water quality conditions include tempering of the adverse condition (decreased temperatures, increased dissolved oxygen), predation protection, and increased foraging opportunities.

A review of the global diversity and natural history of stalked jellyfishes (Cnidaria, Staurozoa)

In this review, we present the current state of biodiversity knowledge for the class Staurozoa (Cnidaria), including richness estimates, geographical and bathymetric distributions, substrate use, feeding, behavior, life cycle, and conservation. Based on non-parametric, statistical incidence estimators, the global inventory of 50 known and accepted species of stalked jellyfishes might be regarded as close to complete, but we discuss possible bias related to the lower research effort applied in the Southern Hemisphere. Most of the species occur at mid-latitudes, presenting a distributional pattern that disagrees with the classic pattern of diversity (higher richness near the Equator). Specimens are frequently found on algae, but they have also been reported attached to rocks, seagrasses, shells, mud, sand, coral/gorgonian, sea cucumber, and serpulid tube. Most of the species are found in the intertidal and shallow subtidal regions, but species of Lucernaria have been reported at more than 3000 m deep. Amphipods and copepods are the prey items most frequently reported, and stauromedusae have been observed being actively preyed upon by nudibranch mollusks and pycnogonids. Apparently, stalked jellyfishes have a high sensitivity to anthropic impacts in the environment, and promotion of the class, one of the least studied among Cnidaria, is perhaps the best possible conservation strategy.

Understory algae and low light reduce recruitment of the habitat-forming kelp Ecklonia radiata

Kelp forests form important habitat in temperate subtidal regions but are threatened by a range of stressors that impact their abundance. In this study, we determined the effect of understory algae, a potential competitor of kelp, on the recruitment of the Australasian kelp, Ecklonia radiata, via their role in reducing light availability for early life-cycle stages of Ecklonia. A field experiment manipulating the abundance of understory algae showed no recruitment of outplanted microscopic sporophytes or naturally recruiting macroscopic sporophytes with a high (> 80%) cover of understory algae. In contrast, both microscopic and macroscopic sporophytes recruited into plots with a medium (40 to 60%) and low (< 20%) cover of understory algae. Light appears to be the important mechanism for the inhibition of kelp recruitment because a high cover of understory algae blocks up to 90% of available light for Ecklonia recruits. A laboratory experiment showed that low light (similar to the levels beneath the understory of high-coverage algal canopies) inhibited Ecklonia gametophyte growth and prevented microscopic sporophyte recruitment. Both high light (similar to levels when there is little understory algal canopy) and high zoospore density resulted in high sporophyte recruitment, suggesting important additive effects of those factors. This study indicates that an increase in the cover of understory algae results in low light, which inhibits Ecklonia sporophyte recruitment. The resilience of kelp will be strongly influenced by recruitment, and our results highlight that a decline in kelp canopy cover which leads to an increase in understory algae can ultimately feedback to negatively affect kelp recruitment.

Fish and Blue Crab Density along a Riprap‐Sill‐Hardened Shoreline: Comparisons with Spartina Marsh and Riprap

AbstractWetland managers have historically considered riprap‐sill structures (a type of “living shoreline” consisting of a rock sill that is placed low in the intertidal zone, with native vegetation planted between the sill and the shore) to be more ecologically sound than the riprap that is traditionally applied for shoreline stabilization in estuaries. However, little research has been conducted to compare the macrofauna associated with riprap‐sill and riprap‐hardened shorelines. Density and diversity of fish and blue crabs Callinectes sapidus were compared via weekly sampling along a riprap‐sill shoreline, a riprap shoreline, and a shoreline fringed with smooth cordgrass Spartina alterniflora marsh in the Delaware Coastal Bays during summer 2010. Seining was conducted to quantitatively sample the shore zone and shallow subtidal regions, and minnow traps were used to determine the presence or absence of fishes in the mid‐ to upper‐intertidal zone of each shoreline type. Temporally persistent differences in macrofaunal density and diversity were evident among the three shoreline types. In terms of fish density and diversity metrics, riprap‐sill was more similar to the smooth cordgrass shoreline than to the traditional riprap shoreline. These results provide evidence for the biological advantage of riprap‐sill over traditional riprap as a shoreline modification structure; spatial confirmation by further studies at different locations is warranted.Received October 27, 2015; accepted March 15, 2016 Published online June 21, 2016

First account on kinorhynchs from Portugal, with the description of two new species: Echinoderes lusitanicus sp. nov. and E. reicherti sp. nov.

ABSTRACTThe first exploration of the kinorhynch meiofauna in Portuguese marine waters has revealed the existence of two undescribed species of the cyclorhagid genus Echinoderes. In the present contribution we describe Echinoderes lusitanicus sp. nov. and Echinoderes reicherti sp. nov., both collected from subtidal regions of the coast of Algarve in the southernmost region of Portugal. Echinoderes lusitanicus sp. nov. is recognized by the presence of tubes on segment 2 in subdorsal and ventrolateral positions, on segment 5 in lateroventral positions, on segment 8 in lateral accessory positions, and on segment 10 in laterodorsal positions. Spines are present in middorsal position on segments 4 to 8, and in lateroventral positions on segments 8 and 9. The females have minute lateral terminal accessory spines. The second species, E. reicherti sp. nov., is characterized by tubes on segment 2 in subdorsal and ventrolateral positions, on segment 5 in lateroventral positions, and segment 8 in sublateral positions. In addition, the species possesses acicular spines in the middorsal position on segment 4, and in lateroventral positions on segments 6 to 9. Morphological aspects such as tube/spine pattern of the trunk or sexually dimorphic traits are discussed and compared with other Echinoderes species showing close resemblance.http://zoobank.org/urn:lsid:zoobank.org:pub:79C25EEE-9064-46F8-95E2-EE493DC82185

남해도 주변 조하대 해역의 대형저서동물 분포

남해도 주변 조하대 해역의 대형저서동물 분포

Diversity of Ascidians from the Great Nicobar Biosphere Reserve (GNBR), India

The Great Nicobar Biosphere Reserve nurtures a diverse amount of life and is very important to the biological diversity of India. Ascidians diversity has been recorded for the first time from the Great Nicobar Biosphere Reserve. In the present study, 15 species of ascidians were noticed in both intertidal and sub-tidal regions of GNBR, belonging to two orders, three suborders, six families and ten genera (Didemnum fulgens, Didemnum vexillum, Didemnum granulatum, Didemnum albidum, Didemnum candidum, Trididemnum cyanophorum, Diplosoma simile, Diplosoma spongiforme, Clavelina oblonga, Aplidium fuscum, Synoicum castellatum, Pycnoclavella diminuta, Ascidia virginea, Ascidiella aspersa and Styela sp.) during the year 2013-2014 of which, the Didemnidae family was recorded with the high diversity of 15 species. Species richness were highly recorded in Bquary Beach and lowly recorded from Campbell Bay. The present data suggests that GNBR coast offers a unique opportunity for future research on the ascidians diversity and ecology assessment. Keywords: Ascidians, Biodiversity, GNBR

Comparison of Symbiodinium populations in corals from subtidal region and tidal pools of northern coasts of Hengam Island, Iran

Coral reefs are integral part of tropical ecosystems and obligatory symbiosis with the genus Symbiodinium has a vital role in resistance and survival of the holobiont. Nine different genetic clades (A to I) have been discovered by molecular techniques. Members of Symbiodinium are ecologically and biogeographically diverse and their distribution patterns are determined by temperature, irradiance, depth, season and latitude however stress-tolerant species might be detected within each clade. Samples of four coral species from subtidal region in the north of Hengam Island, Persian Gulf (PG) and its tidal pools were analyzed by internal transcribed spacer of ribosomal DNA and by the aid of Denaturing Gradient Gel Electrophoresis (DGGE) to compare the differences in populations of their symbionts. The results showed that some subtidal colonies of one species harbored less tolerant subtypes of Symbiodinium subclade C7. Nonetheless, clade D Symbiodinium was the most dominant symbiotic clade in both tidal pool and subtidal coral colonies. A novel subtype of subclade D1 Symbiodinium was also detected in some coral colonies and was inferred as subclade D1.PG Symbiodinium. The prevalence of clade D Symbiodinium might reflect corals response to extreme environmental stresses of tidal pools and the northern PG itself that coral inhabitants have to cope with.

Pyrosequencing characterization of the microbiota from Atlantic intertidal marine sponges reveals high microbial diversity and the lack of co-occurrence patterns.

Sponges are ancient metazoans that host diverse and complex microbial communities. Sponge-associated microbial diversity has been studied from wide oceans across the globe, particularly in subtidal regions, but the microbial communities from intertidal sponges have remained mostly unexplored. Here we used pyrosequencing to characterize the microbial communities in 12 different co-occurring intertidal marine sponge species sampled from the Atlantic coast, revealing a total of 686 operational taxonomic units (OTUs) at 97% sequence similarity. Taxonomic assignment of 16S ribosomal RNA tag sequences estimated altogether 26 microbial groups, represented by bacterial (75.5%) and archaeal (22%) domains. Proteobacteria (43.4%) and Crenarchaeota (20.6%) were the most dominant microbial groups detected in all the 12 marine sponge species and ambient seawater. The Crenarchaeota microbes detected in three Atlantic Ocean sponges had a close similarity with Crenarchaeota from geographically separated subtidal Red Sea sponges. Our study showed that most of the microbial communities observed in sponges (73%) were also found in the surrounding ambient seawater suggesting possible environmental acquisition and/or horizontal transfer of microbes. Beyond the microbial diversity and community structure assessments (NMDS, ADONIS, ANOSIM), we explored the interactions between the microbial communities coexisting in sponges using the checkerboard score (C-score). Analyses of the microbial association pattern (co-occurrence) among intertidal sympatric sponges revealed the random association of microbes, favoring the hypothesis that the sponge-inhabiting microbes are recruited from the habitat mostly by chance or influenced by environmental factors to benefit the hosts.

Large-scale dam removal on the Elwha River, Washington, USA: Coastal geomorphic change

Two dams on the Elwha River, Washington State, USA trapped over 20millionm3 of mud, sand, and gravel since 1927, reducing downstream sediment fluxes and contributing to erosion of the river's coastal delta. The removal of the Elwha and Glines Canyon dams, initiated in September 2011, induced massive increases in river sediment supply and provided an unprecedented opportunity to examine the geomorphic response of a coastal delta to these increases. Detailed measurements of beach topography and nearshore bathymetry show that ~2.5millionm3 of sediment was deposited during the first two years of dam removal, which is ~100 times greater than deposition rates measured prior to dam removal. The majority of the deposit was located in the intertidal and shallow subtidal region immediately offshore of the river mouth and was composed of sand and gravel. Additional areas of deposition include a secondary sandy deposit to the east of the river mouth and a muddy deposit west of the mouth. A comparison with fluvial sediment fluxes suggests that ~70% of the sand and gravel and ~6% of the mud supplied by the river was found in the survey area (within about 2km of the mouth). A hydrodynamic and sediment transport model, validated with in-situ measurements, shows that tidal currents interacting with the larger relict submarine delta help disperse fine sediment large distances east and west of the river mouth. The model also suggests that waves and currents erode the primary deposit located near the river mouth and transport sandy sediment eastward to form the secondary deposit. Though most of the substrate of the larger relict submarine delta was unchanged during the first two years of dam removal, portions of the seafloor close to the river mouth became finer, modifying habitats for biological communities. These results show that river restoration, like natural changes in river sediment supply, can result in rapid and substantial coastal geomorphological responses.

Numerical study of sediment transport on a tidal flat with a patch of vegetation

To understand how vegetation canopies affect sediment transport on tidal flats, a numerical study of tidal flow and sediment transport on an idealized tidal flat with a patch of vegetation is conducted. The numerical model is firstly validated by laboratory measurements of flow and sediment deposition in a partially vegetated open channel. The idealized study shows that a finite patch of vegetation may produce circulation on the tidal flat with converging flow during flood and diverging flow during ebb. The vegetation patch can also generate a tidal phase lag between the vegetated and bare flats. Tidal currents in both zones are asymmetric, with stronger flood current in the vegetated zone and stronger ebb current on the bare flat. The duration of ebb is longer than that of flood. Computed sediment concentration on the bare flat is higher during ebb due to stronger ebb current and larger bottom shear stress. This is in contrast to the tidal flat without a vegetation canopy, where suspended sediment concentration is higher during flood. On the tidal flat without a vegetation canopy, landward net sediment transport occurs on the upper flat, while seaward net sediment transport occurs on the lower flat and subtidal region. On the partially vegetated tidal flat, however, net sediment transport on both the upper and lower flats are in seaward direction. It increases with increasing vegetation density. Alongshore net sediment flux converges inside the canopy and diverges on the bare flat. Sediment exchange rate between the vegetated and bare flats increases with decreasing vegetation density and sediment settling velocity.

Does Encope emarginata (Echinodermata: Echinoidea) affect spatial variation patterns of estuarine subtidal meiofauna and microphytobenthos?

Foraging macrofauna, such as the sand dollar Encope emarginata, can modify sediment properties and affect spatial distribution patterns of microphytobenthos and meiobenthos at different spatial scales. We adopted a spatial hierarchical approach composed of five spatial levels (km, 100sm, 10sm, 1sm and cm) to describe variation patterns of microphytobenthos, meiobenthos and sediment variables in shallow subtidal regions in the subtropical Paranaguá Bay (Southern Brazil) with live E. emarginata (LE), dead E. emarginata (only skeletons — (DE), and no E. emarginata (WE). The overall structure of microphytobenthos and meiofauna was always less variable at WE and much of variation at the scale of 100sm was related to variability within LE and DE, due to foraging activities or to the presence of shell hashes. Likewise, increased variability in chlorophyll-a and phaeopigment contents was observed among locations within LE, although textural parameters of sediment varied mainly at smaller scales. Variations within LE were related to changes on the amount and quality of food as a function of sediment heterogeneity induced by the foraging behavior of sand dollars. We provide strong evidence that top-down effects related to the occurrence of E. emarginata act in synergy with bottom-up structuring related to hydrodynamic processes in determining overall benthic spatial variability. Conversely, species richness is mainly influenced by environmental heterogeneity at small spatial scales (centimeters to meters), which creates a mosaic of microhabitats.

A study on the biodiversity of benthic invertebrates in the waters of Seogwipo, Jeju Island, Korea

The biodiversity of benthic invertebrates in the intertidal and subtidal regions of Gapado, Beomseom, and Munseom islets was surveyed twice in May and September 2013 to study the state of biodiversity in Seogwipo, Jeju Island. As a result, a total of 77 species, 46 families, 25 orders, 14 classes, and nine phyla of benthic invertebrates were found. The species which were found, by taxon, consisted of the following: 26 species of Cnidaria (34%), 24 species of Mollusca (31%), seven species of Chordata (9%), six species of Arthropoda (8%), six species of Porifera (8%), five species of Echinodermata (7%), one species of Bryozoa (1%), one species of Annelida (1%), and one species of Ctenophora (1%).

The seafloor after a bolide impact: sedimentary and biotic signatures across the Late Devonian carbonate platform following the Alamo Impact Event, Nevada, USA

Eighty measured stratigraphic sections across the Late Devonian carbonate platform of Nevada (USA) document the uppermost terminal Alamo Breccia and overlying sediments, which record the waning energy at the end of an impact and the recolonization of the post-impact seafloor. Four sedimentary styles of terminal breccia, recognized by the continuity of normal grading versus reworking, and dolomitization, define patterns of sedimentary accommodation across the platform. Examined in combination with the first post-impact facies, the field area can be divided into deep subtidal, shallow subtidal, and peritidal zones with increased distance from the inferred crater center. Farthest away, peritidal outcrops have very low accommodation, and the terminal breccia is physically reworked and dolomitized. Biotic signals are rare in this zone. However, we find rare but exceptional deposits of impact fallout lapilli at or above the top of the breccia. The shallow subtidal region records reworked and pristine grading of the terminal breccia, which at several locations document burrowing directly into the top of the Alamo Breccia, confirming infaunal recolonization prior to post-impact sediment accumulation. Rare occurrences of erosional terminal breccia produced rockgrounds at the seafloor, some showing evidence of bioerosion. Deeper subtidal localities, closest to the crater center, preserve the thickest, continuously graded terminal breccias owing to high accommodation at the end of the event. Body and trace fossils are common in the first overlying lithofacies, although the abundance of oxidized firmground surfaces in deep water settings suggest these deposits were sediment-starved and fossil assemblages are strongly time-averaged.