Sandy Bottom Habitat Research Articles

Multidimensional comparison of underwater soundscapes using the soundscape codea).

The soundscape of a given habitat is a product of its physical environment, human activity, and presence of soniferous marine life, which can be used to understand ecosystem processes, habitat quality, and biodiversity. Shallow coral habitats are hotspots of biodiversity and marine life. Deep-sea coral environments, in comparison, are generally poorly understood. Four soundscapes along the U.S. Outer Continental Shelf (OCS) and one soundscape from the Great Barrier Reef were quantified to explore how differences in habitat, depth, and substrate manifest acoustically. Comparisons were made between (1) deep, cold-water and shallow, warm-water coral reefs and (2) deep-sea coral and sandy bottom habitats. Application of the soundscape code to recordings in each location seeded cluster analyses of soundscape metrics and an assessment of daily trends to quantitatively compare the soundscapes. The shallow, tropical reef soundscape differed from the deep-sea soundscapes in amplitude and impulsiveness. Differences in soundscape properties among the deep-sea soundscapes suggested cold-water coral sites produce different soundscapes than the deep sites without live hard bottom. This initial assessment of deep-sea soundscapes along the U.S. OCS provides baseline acoustic properties in a region likely to experience changes due to climate and human use.

Multidimensional comparison of ocean soundscape properties across depth and substrate type

The local soundscape is determined by its physical environment, human activity, and presence of soniferous marine life and, therefore, provides insight on ecosystem processes, habitat quality, and biodiversity. Shallow coral habitats in tropical environments are hotspots of biodiversity and marine life. Deep-sea coral environments along the southeastern U.S. provide important habitat for a variety of marine animals but are generally poorly understood. An innovative Soundscape Code methodology for quantitatively characterizing soundscapes was applied to passive recordings from four locations along the US Outer Continental Shelf (OCS) and one from the Great Barrier Reef to assess how differences in habitat, depth, and substrate manifest acoustically. Comparisons were made between (1) deep, cold-water and shallow, warm-water coral reefs and (2) deep-sea coral and sandy bottom habitats. The shallow, tropical reef soundscape differed from the deep-sea soundscapes in amplitude and impulsiveness. Differences in soundscape properties among the deep-sea soundscapes suggest deep-sea coral sites produce different soundscapes than the deep sites without live hardbottom. Biologic and anthropogenic signals influenced the deep-sea soundscapes and represent fundamental differences in habitat. This initial assessment of deep-sea soundscapes along the US OCS provides baseline acoustic properties in a region likely to experience changes in climate and human use.

First description of deep benthic habitats and communities of oceanic islands and seamounts of the Nazca Desventuradas Marine Park, Chile

Seamounts and oceanic islands of the Chilean Exclusive Economic Zone at the intersection of the Nazca and Salas y Gómez ridges lie within one of the least explored areas in the world. The sparse information available, mainly for seamounts outside Chilean jurisdiction and shallow-water fauna of the Desventuradas Islands, suggests that the area is a hotspot of endemism. This apparent uniqueness of the fauna motivated the creation of the large Nazca-Desventuradas Marine Park (NDMP, ~ 300,000 km2) around the small islands San Felix and San Ambrosio in 2015. We report for the first time a detailed description of benthic microhabitats (i.e., centimeter to meter scale), macrohabitats (i.e., meter to kilometer-scale) and associated megafauna within the NDMP. Descriptions were based on analysis of fauna collected by trawling and ROV video observations from ~ 50 to 370 m depth. Rocky, coarse sand and silty sediment bottom habitats were observed at island slopes. In contrast, rocky and coarse sandy bottom habitats with a predominance of rhodoliths, thanatocoenosis, and other biogenic components were observed at seamounts. Mobile fauna and predators dominated the oceanic islands and nearby seamounts, whereas seamounts farther from the islands were dominated by sessile and hemisessile fauna that were mainly suspension and deposit feeders. Based on the register of 118 taxonomic units, our results provide an expanded and updated baseline for the benthic biodiversity of NDMP habitats, which seemed pristine, without evidence of trawling or anthropogenic debris.

Natural History Observations of Hawaiian Garden Eels, Gorgasia hawaiiensis (Congridae: Heterocongrinae), from the Island of Hawai‘i

Garden eels occur worldwide in the tropics, but little is known about their biology and ecology. We studied Hawaiian garden eel ( Gorgasia hawaiiensis ) colonies near Kawaihae, Hawai‘i, to investigate multiple aspects of basic biology of this species. Colonies of G. hawaiiensis occurred at depths from 16 to 36 m in soft-bottom habitat adjacent to rocky reefs. Highest burrow densities (up to 40 eels m−2) were in shallower water, and large (~10 mm diameter) burrows were more abundant, less dense, and commonly found in pairs in deeper water. Eels emerged around sunrise and withdrew and covered burrow entrances around sunset. Age was estimated from annual rings in sectioned otoliths ( n = 17) and modeled to suggest fast growth to a maximum size of ~600 mm total length and a maximum age of 6 yr. Prey size and eel anatomy suggest that these fish feed by ingesting planktonic prey and processing them in the esophagus. The most common food items were small ( G. hawaiiensis is abundant, has a high population turnover rate, and may enrich sandy-bottom habitat within their beds by facilitating energy flow from the water column to the benthos.

Seasonal Variability In Subtidal Fish Assemblages Inhabiting Sandy-Bottom Habitats Off Humboldt Bay, California

Abstract This study documents the seasonal fine-scale distribution, species richness, and abundance of subtidal fish species inhabiting sandy-bottom habitats in areas adjacent to Humboldt Bay, California. In total, 3 sampling areas, 2 located 5-km offshore, and 1 located 1-km offshore, were sampled quarterly for 1 y. Flatfish species (families Pleuronectidae and Bothidae) were the most common finfish sampled, although seasonal and spatial patterns varied among individual species. For instance, the abundance and size of English Sole (Parophrys vetulus) and Pacific Sanddab (Citharichthys sordidus) varied across both seasons and sampling areas, which may be attributed to their ontogenetic migration to offshore adult habitat. Species such as Starry Flounder (Platichthys stellatus) and Butter Sole (Isopsetta isolepis), did not vary seasonally, but did differ across sampling areas, likely as a function of depth. Although not the primary focus of our study, we include the abundance and diversity of invertebrates...

Establishment and management of fisheries refugia in Phu Quoc Marine Protected Area, Vietnam

and management of fisheries refugia have recently been recognized as important tools in sustainable use/ management of fish stocks and their associated habitats. To initiate the fisheries refugia management approach in Phu Quoc, several activities were conducted to collect baseline information for establishment of fisheries refugia in Phu Quoc Archipelago since 2007, including local consultations and field surveys involving local communities and concerned stakeholders. Site selection for the establishment of model/ fisheries refugia was based on scientific data and consultations with local communities and based on criteria of habitat representativeness, target species diversity and abundance and site management potential. Results from the baseline surveys recorded 11 spawning and nursery grounds of several target species including; octopus ( Octopus dollfusi), cuttlefish (Sepioteuthis lessoniana ), the Strombus shell (Strombus canarium), swimming crab (Portunus pelagicus), seahorses (Hippocampus spp.), rabbitfishes (Siganus spp.) associated with seagrass habitat and squids (Loligo spp.) associated with sandy bottom habitat. In the coral reef habitats, there were 10 locations where nursery grounds of barred-cheek coral trout (Plectropomus maculatus) were found in the waters surrounding most of the group of islands (An Thoi) in the southern part of Phu Quoc big island. Two pilot sites were selected for fisheries refugia management, one to protect the nursery grounds of grouper associated with coral reef habitats at Hon Roi fishing village and the other to protect the spawning/nursery grounds of the Strombus shell, octopus, swimming crab and seahorses associated with the sea

Parasites in subyearling Chinook salmon (Oncorhynchus tshawytscha) suggest increased habitat use in wetlands compared to sandy beach habitats in the Columbia River estuary

Many estuaries in the Pacific Northwest have been severely altered reducing wetlands habitat and resulting in an interest in their importance as rearing areas for juvenile salmon. To examine differences in habitat use during residency in the Columbia River estuary, we examined parasite communities acquired through food web interactions in subyearling Chinook salmon (Oncorhynchus tshawytscha) collected from four different habitat types in May and July of 2004 and 2005. Collections were made from two sandy bottom habitat types in the tidal freshwater and marine mixing areas of the estuary. These were compared to two wetlands types: one composed of scrub and shrub vegetation and another with emergent vegetation. Parasite assemblages differed among habitats suggesting differences in salmon feeding opportunities and rearing behaviors. In both years, the nematode, Hysterothylacium aduncum and the acanthocephalan, Echinorhynchus lageniformis, which use intermediate hosts found in the estuary, were more prevalent in lower wetlands suggesting increased feeding by salmon in these habitats. The differences in parasite assemblages among habitats suggests a variety of rearing and migration patterns through the Columbia River estuary and the increased prevalences of some parasites in the wetlands show that these habitats can be important feeding grounds for salmon.

Alternative Reproductive Tactics in the Shell-Brooding Lake Tanganyika Cichlid Neolamprologus brevis.

Alternative reproductive tactics (ARTs) are found in several Lake Tanganyika shell-brooding cichlids. Field studies were conducted in the Wonzye population to examine reproductive ecology and ARTs in the Lake Tanganyika shell-brooding cichlid Neolamprologus brevis. We discovered that this fish occurred in both rocky- and sandy-bottom habitats, but in rocky habitats, brood-caring females exclusively occurred in shell-patches that another cichlid species created. All N. brevis of both sexes in the patches were sexually mature, whereas immature males and females with unripe eggs were found frequently in sandy-bottom habitats. Males in sandy-bottom habitats were smaller, but fed more frequently and were in better somatic condition than males in the patches. Similar tendency was found in females. This indicates that N. brevis uses different habitats depending on the stage of its life history, with migration from sandy-bottom habitats to the shell-patches for reproduction. Males in the patches exhibited different behavior patterns: floating above the patches and lying in the patches. The former was larger, more aggressive, and invested less in gonads (relative to body size) than the latter. These results accord with those of other shell-brooding Lake Tanganyika cichlids with ARTs, and they therefore suggest the presence of ARTs in N. brevis.

Incomplete cryptic speciation between intertidal and subtidal morphs of Acrocnida brachiata (Echinodermata: Ophiuroidea) in the Northeast Atlantic

The brittle-star Acrocnida brachiata (Montagu) lives in sandy-bottom habitat of both intertidal and subtidal zones along the coasts of the northwestern Europe. An allozyme frequency-based survey (five enzyme loci) was combined with a mitochondrial (mt) COI haplotype analysis (598-bp sequences) on 17 populations to trace back past colonization pathways from the actual population structure of the species. Both genetic markers display a sharp genetic break between intertidal (clade I) and subtidal populations (clade S). This break corresponds to an allele frequency inversion at three enzyme loci (Hk, Pgm and Pgi) and a deep divergence of about 20% in mtCOI sequences between most of the intertidal populations and other samples. The geographic distribution of clade I seems to be more restricted than clade S as it is absent from the intertidal of the eastern English Channel and North Sea and may be replaced by clade S in south Brittany. Applying previously published rates of mutation, divergence between the two clades is estimated to pre-date 5 million years ago and may be due to allopatric speciation processes at the Mio-Pliocene transition. The occurrence of putative hybrids in a few localities, however, suggests incomplete cryptic speciation with secondary contact zones. The relative importance of colonization history vs. habitat specialization are discussed in the light of neutral evolution as tested from mtCOI gene sequences. While differential selection seems to have contributed little to the separation of the lineages, it may have played a role in the emergence of adaptive polymorphisms in the hybrid zone. Furthermore, congruent spatial patterns of differentiation were observed in both clades suggesting a recent increase in population size. These findings are in agreement with a recent expansion of the populations during or after the formation of the English Channel, from a southern refuge for the subtidal clade whereas the intertidal clade may have persisted further north. As previously suspected for a species with a very short pelagic larval phase, contemporary gene flow between distant or adjacent populations appears to be extremely reduced or even absent.

Deforestation alters the hydraulic and biogeochemical characteristics of small lowland Amazonian streams

AbstractWe investigated how clearing of the tropical rainforest for cattle pasture along small, terra firme lowland streams in the Brazilian Amazon influenced stream hydraulic characteristics, solute concentrations and uptake of dissolved inorganic nitrogen and phosphorus. Measurements of stream channel structure, hydraulic properties and nutrient uptake were obtained from short‐term conservative and non‐conservative solute injections and an in‐stream transport model in two watersheds with pairs of similar‐sized forest and pasture streams in Rondônia. The pasture stream channels were deeper and had a lower cover of sandy bottom habitat and a higher cover of aquatic grass habitat than the forest streams. The pasture streams had larger transient storage zones, higher ratios of transient to channel storage and a shorter hydraulic uptake length than the forest streams. The pasture streams had lower concentrations of dissolved oxygen and NO3− and higher concentrations of dissolved Fe2+. Forest streams exhibited no NO3− uptake, but one pasture stream took up NO3− while the other did not. Uptake of NH4+ was low and variable among streams. Uptake velocities and rates of PO43− were greater in pasture streams compared to those in forest streams. In all streams, uptake lengths for NO3−, NH4+ and PO43− were long and indicated generally lower rates of uptake than in most comparably sized temperate forest streams. Uptake lengths or velocities were not correlated with stream transient storage, suggesting that other factors, such as hypoxia in pasture streams, controlled nutrient uptake. The structural differences are typical for the region, suggesting that deforestation may be altering stream hydrology and biogeochemistry over many thousands of kilometres of primary and secondary stream channels in the Amazon Basin. A better understanding of the extent and distribution of altered hydraulic and biogeochemical function in small streams is required to assess the importance of these changes for larger river networks in the Amazon basin. Copyright © 2006 John Wiley & Sons, Ltd.

Ecological and geochemical characteristics of bottom habitats at the northern Jordanian coast of the Gulf of Aqaba

A detailed study to assess the environmental conditions of the benthic habitats at the northern tip of the Gulf of Aqaba has been carried out during the summer of 2003. The texture, geochemical, and biogenic characteristics of bottom sediments as well as a description and distribution of corals, seagrass, fish species, and fish assemblages have been investigated. Results showed that the sea bottom at the study site is mainly a non-coralline sandy bottom covered with seagrass. Well-developed seagrass beds covered about 70–98% of the bottom. No coral cover was recorded. This is to be expected because of the absence of hard substrate and because of high loads of suspended matter. The seagrass habitat in the area serves as important nursery grounds for the fish larvae and hosts sea urchins and sea cucumbers. The bottom sand in the area was undisturbed, animal tracks were rare, but bioturbated holes and mounds were abundant. Bottom surface sediments were fine-grained, black with high quartz, feldspar, and mica, and low in mud content. Chemically, these sediments had low calcium carbonate, organic nitrogen, and high total phosphorus concentrations, suggesting that the sediment mineral composition is derived from existing metamorphic rocks, by weathering and erosion. The biogenous part of the sediments was mainly calcium carbonate, consisting of shells or coverings of some micro- and macro-organisms. The number and diversity of fish species inhabiting the survey site are typical of seagrass-bed sandy-bottom habitats. Some of the fish species observed are characteristic of this site and very rarely found elsewhere on the Jordanian coast. About half the fish population in the area belong to six families: Labridae (12%), Pomacentridae (7%), Mullidae (7.%), Apoginidae (6%), Chaetodontidae (6%), and Gobiidae (6%).

Environmental and benthic habitat factors structuring the spatial distribution of a summer infralittoral fish assemblage in the north-western Mediterranean Sea

Patterns of distribution of a Mediterranean fish assemblage, with special attention to juvenile labrids, were studied at different depths on the basis of their relationships with environmental and benthic habitat features on a rocky coast at Marseille, south-eastern France. Fish species were distributed according to depth, with juveniles and small individuals being found in shallow waters, whereas larger individuals were found in deeper waters. However, depth by itself was not a significant factor in explaining fish species pattern, whereas sandy bottom habitat was significant. The most significant factors explaining fish species distribution were small and large blocks, and rock cover. Juvenile labrids, such as the most abundant ones Coris julis and Symphodus ocellatus, were only rarely observed deeper than 10 m, and the distribution of these juveniles was mainly correlated with a cover of macroalgae, rubble and small blocks. Fish density and fish biomass were higher in shallow than in deeper waters, although some species displayed an opposite pattern, such as the adult of C. julis and Diplodus sargus. The most significant factors explaining the fish density pattern found were the presence of macroalgae, Posidonia oceanica sea grass and sand cover. Among environmental factors assessed in this study, exposure to dominant winds was never significant, either for the whole fish assemblage or for juvenile labrids, or for the communities at any of the depth strata investigated. Depth was a significant factor influencing the distribution of juvenile labrids, whereas its significance in explaining fish density was lower. Bottom slope was generally more significant than depth, and thus constituted the most significant environmental factor. Benthic habitat characteristics were all significant, except for rubble cover, in explaining both fish species and fish density distributions. However, the amplitude of the relationships between substrate variables and fish assemblages was dependent on the descriptor studied (i.e. species distribution, including considerations of fish sizes, and fish density), suggesting that extrapolation of a particular relationship to other components of a fish assemblage would most likely be unfounded. Our results as a whole indicate that benthic habitat use by fish on Mediterranean rocky infralittoral coast is clearly non-random, and suggest that differences in habitat and/or environmental characteristics have significant effects at a small spatial scale on these fish assemblages.

Distribution and abundance of thraustochytrids in different Mediterranean coastal habitats

Habitat, seasonality and species distribution of the marine fungoid protists, thraus- tochytrids, were investigated in a coastal area of the Ligurian Sea (NW Mediterranean). Three habi- tats (the sandy surf area, the middle of a 5 m seawater column, and its underlying sandy sea bottom) were monitored monthly for 1 yr. Thraustochytrids in the surf and sea-bottom sandy samples yielded average densities of 4.4 ± 4 and 6.1 ± 5.3 × 10 4 cells l -1 , respectively. In both sandy habitats, a similar seasonal trend was observed: the highest densities were recorded in late spring, while a significant drop in densities occurred during the autumn-winter period. In the water column, the density of thraustochytrids was much lower, 1.3 ± 1 × 10 2 cells l -1 and did not show significant seasonal varia- tions. A positive relationship between organic matter and thraustochytrid densities occurred in the sandy sea bottom. Among the nutrients assessed in the water column, only total phosphorus was related to variations of thraustochytrid densities. The 3 habitats analyzed showed marked differences in species number and assemblage. A higher number of species were found in the sandy sea bottom than in the sandy surf area and in the seawater column. The genus Thraustochytrium was the most abundant in the sandy bottom habitat. Among Thraustochytrium species, those characterized by spo- rangia with proliferation bodies were dominant. Species of the genus Schizochytrium, typically form- ing a cluster of sporangia, were dominant in the sandy surf area. Here, the possible ecological signif- icances of these species' features are discussed.

Sandy bottom macroinvertebrates in two moderately polluted stations of the River Treia (Central Italy) : structural and functional organization

A study on sandy bottom macroinvertebrates in two moderately polluted stations of the River Treia (Central Italy) was carried out in order to analyze their structural and functional feeding organization. A total of 60 taxa were collected during the study. Oligochaeta, Gammaridae, Diptera-Chironomidae and Ephemeroptera constituted the bulk of the total fauna. Most of the taxa were typical of sandy bottom habitats and moderate current flow. Collectors and shredders were the dominant feeding groups in both stations. Predators were strongly and positively correlated with the abundances of collectors and shredders (potential prey). Moreover, the direct relationships found between taxonomic and trophic diversities or between taxonomic and trophic evenness suggest a relatively good partitioning of food resources among the taxa. The most common organisms found in both stations were typical of mesosaprobic environments, indicating that the macrofauna of fine sediments seems to be suitable for detecting moderate organic pollution in rivers.