Submarine groundwater discharge in Osaka Bay, Japan

Submarine groundwater discharge (SGD) rates in Osaka Bay were continuously measured and analyzed to evaluate seawater–groundwater interactions. Fast Fourier transfer and power spectrum density methods were applied to analyze the dominant periods of the SGD variations. Diurnal and semidiurnal periods of SGD variation were found, and they were caused by tidal effects. According to the separation of SGD into fresh and recirculated water components using automated seepage meter measurements and terrestrial groundwater flow analyses, the fresh groundwater component in SGD was evaluated to be in the range 4%–29% at Tannowa, Osaka. Therefore, SGD rates depend mainly on the volume of recirculated seawater. Correlation analyses between SGD and sea level show that SGD is delayed by 4h after sea level changes.     

An assessment of karstic submarine groundwater and associated nutrient discharge to a Mediterranean coastal area (Balearic Islands, Spain) using radium isotopes

Short and long-lived radium isotopes (²²³Ra, ²²⁴Ra, ²²⁶Ra, ²²⁸Ra) were used to quantify submarine groundwater discharge (SGD) and its associated input of inorganic nitrogen (NO₃ ^?), phosphorus (PO₄ ^3?) and silica (SiO₄ ^4?) into the karstic Alcalfar Cove, a coastal region of Minorca Island (Western Mediterranean Sea). Cove water, seawater and groundwater (wells and karstic springs) samples were collected in May 2005 and February 2006 for radium isotopes and in November 2007 for dissolved inorganic nutrients. Salinity profiles in cove waters suggested that SGD is derived from shallow brackish springs that formed a buoyant surface fresh layer of only 0.3 m depth. A binary mixing model that considers the distribution of radium activities was used to determine the cove water composition. Results showed that cove waters contained 20% brackish groundwater; of which 6% was recirculated seawater and 14% corresponded to freshwater discharge. Using a radium-derived residence time of 2.4 days, a total SGD flux of 150,000 m³ year^?1 was calculated, consisting of 45,000 m³ year^?1 recirculated seawater and 105,000 m³ year^?1 fresh groundwater. Fresh SGD fluxes of NO₃ ^?, SiO₄ ^4? and PO₄ ^3? were estimated to be on the order of 18,000, 1,140 and 4 μmol m^?2 day^?1, respectively, and presumably sustain the high phytoplankton biomass observed in the cove during summer. The total amount of NO₃ ^? and SiO₄ ^4? supplied by SGD was higher than the measured inventories in the cove, while the reverse was true for PO₄ ^3?. These discrepancies are likely due to non-conservative biogeochemical processes that occur within the subterranean estuary and Alcalfar Cove waters.     

On the possibility for generic modeling of submarine groundwater discharge

We simulate large-scale dynamics of submarine groundwater discharge (SGD) in three different coastal aquifers on the Mediterranean Sea. We subject these aquifers to a wide range of different groundwater management conditions, leading to widely different net groundwater drainage from land to sea. The resulting SGD at steady-state is quantifiable and predictable by simple linearity in the net land-determined groundwater drainage, defined as total fresh water drainage minus groundwater extraction in the coastal aquifer system. This linearity appears to be general and independent of site-specific, variable and complex details of hydrogeology, aquifer hydraulics, streamlines and salinity transition zones in different coastal systems. Also independently of site-specifics, low SGD implies high seawater content due to seawater intruding into the aquifer and mixing with fresh groundwater within a wide salinity transition zone in the aquifer. Increasing SGD implies decreasing seawater content, decreased mixing between seawater and fresh groundwater and narrowing of the salinity transition zone of brackish groundwater in the aquifer.     

Groundwater and pore water inputs to the coastal zone

Both terrestrial and marine forces drive underground fluid flows in the coastal zone. Hydraulic gradients on land result in groundwater seepage near shore and may contribute to flows further out on the shelf from confined aquifers. Marine processes such as tidal pumping and current-induced pressure gradients may induce interfacial fluid flow anywhere on the shelf where permeable sediments are present. The terrestrial and oceanic forces overlap spatially so measured fluid advection through coastal sediments may be a result of composite forcing. We thus define “submarine groundwater discharge” (SGD) as any and all flow of water on continental margins from the seabed to the coastal ocean, regardless of fluid composition or driving force. SGD is typically characterized by low specific flow rates that make detection and quantification difficult. However, because such flows occur over very large areas, the total flux is significant. Discharging fluids, whether derived from land or composed of re-circulated seawater, will react with sediment components. These reactions may increase substantially the concentrations of nutrients, carbon, and metals in the fluids. These fluids are thus a source of biogeochemically important constituents to the coastal ocean. Terrestrially-derived fluids represent a pathway for new material fluxes to the coastal zone. This may result in diffuse pollution in areas where contaminated groundwaters occur. This paper presents an historical context of SGD studies, defines the process in a form that is consistent with our current understanding of the driving forces as well as our assessment techniques, and reviews the estimated global fluxes and biogeochemical implications. We conclude that to fully characterize marine geochemical budgets, one must give due consideration to SGD. New methodologies, technologies, and modeling approaches are required to discriminate among the various forces that drive SGD and to evaluate these fluxes more precisely.     

A hydrogeologic model of submarine groundwater discharge: Florida intercomparison experiment

A hydrogeologic model of submarine groundwater discharge (SGD) to the near-shore environment at a site on the northeast Gulf of Mexico has been developed to provide a basis for comparison with measurements of SGD made using seepage meters, and with estimates derived from chemical tracers. The hydrogeologic model incorporates the seaward movement of fresh water and the recirculation of sea water at the fresh water–salt water interface. The hydrostratigraphy at the site includes the Surficial Aquifer, a thin confining unit known as the Intracoastal Formation, and the underlying Upper Floridan Aquifer. It is not possible to explain either the magnitude or spatial distribution of SGD recorded by the seepage meters, or the magnitude of SGD estimated using radium and radon tracers, if only steady state flow in the Surficial Aquifer is considered. Nor does it appear likely that the difference between the model-based prediction of SGD and the field-based estimates can be fully resolved by leakage across the Intracoastal Formation from a source in the Floridan Aquifer. These results suggest that processes driven by variations in fluid pressure in the marine water column, which occur on a variety of time scales, be examined to quantify their contribution to fluid circulation within and discharge from that segment of the Surficial Aquifer located beyond the low tide line.     

Dehydration and drinking responses in a pelagic sea snake

Recent investigations of water balance in sea snakes demonstrated that amphibious sea kraits (Laticauda spp.) dehydrate in seawater and require fresh water to restore deficits in body water. Here, we report similar findings for Pelamis platurus, a viviparous, pelagic, entirely marine species of hydrophiine ("true") sea snake. We sampled snakes at Golfo de Papagayo, Guanacaste, Costa Rica and demonstrated they do not drink seawater but fresh water at variable deficits of body water incurred by dehydration. The threshold dehydration at which snakes first drink fresh water is -18.3 ± 1.1 % (mean ± SE) loss of body mass, which is roughly twice the magnitude of mass deficit at which sea kraits drink fresh water. Compared to sea kraits, Pelamis drink relatively larger volumes of water and make up a larger percentage of the dehydration deficit. Some dehydrated Pelamis also were shown to drink brackish water up to 50% seawater, but most drank at lower brackish values and 20% of the snakes tested did not drink at all. Like sea kraits, Pelamis dehydrate when kept in seawater in the laboratory. Moreover, some individuals drank fresh water immediately following capture, providing preliminary evidence that Pelamis dehydrate at sea. Thus, this widely distributed pelagic species remains subject to dehydration in marine environments where it retains a capacity to sense and to drink fresh water. In comparison with sea kraits, however, Pelamis represents a more advanced stage in the evolutionary transition to a fully marine life and appears to be less dependent on fresh water.     

Submarine Groundwater Discharge as a nitrogen source to the Ria Formosa studied with seepage meters

Submarine Groundwater Discharge (SGD) has been frequently ignored as a nutrient source to marine ecosystems because it is difficult to identify and quantify. However, recent studies show its ubiquity and ecological importance to the coastal zone, particularly when associated with contaminated continental aquifers. The Ria Formosa is a coastal lagoon located in the south of Portugal and surrounded by an intensely farmed area. Following a 12-month field study using seepage meters, we identified groundwater discharge in the intertidal zone of the lagoon. The seeping fluid was a mixture of two water types: one with low salinity and high nitrate concentration and another similar to local seawater. Based on the integration of monthly seepage rate measurements throughout the year, we estimate the mean discharge of submarine groundwater into the lagoon to be 3.6 m³ day⁻¹ per linear meter of coastline with freshwater contributions (per volume) ranging from 10% to 50%. The results of this study suggest a continental origin for the freshwater component, thus linking the biogeochemical cycles in the lagoon to anthropogenic activities taking place in the neighboring coastal plain. We further identify SGD as an important nutrient source to the Ria Formosa, estimating annual loads of 36.2 mol (0.507 kg) of Nitrogen, 1.1 mol (0.034 kg) of Phosphorus and 18.6 mol (0.522 kg) of Silicon per meter of coastline. Based on these results, we suggest that SGD is a potential contributor to the observed nutrification status of the Ria Formosa lagoon. All the authors were previously in Biogeochemistry Research Group, CIMA/IMAR (Centro de Investigacao Marinha e Ambiental/Instituto do Mar), Campus de Gambelas, 8000, Faro.     

The typological approach to submarine groundwater discharge (SGD)

Coastal zone managers need to factor submarine groundwater discharge (SGD) in their integration. SGD provides a pathway for the transfer of freshwater, and its dissolved chemical burden, from the land to the coastal ocean. SGD reduces salinities and provides nutrients to specialized coastal habitats. It also can be a pollutant source, often undetected, causing eutrophication and triggering nuisance algal blooms. Despite its importance, SGD remains somewhat of a mystery in most places because it is usually unseen and difficult to measure. SGD has been directly measured at only about a hundred sites worldwide. A typology generated by the Land–Ocean Interaction in the Coastal Zone (LOICZ) Project is one of the few tools globally available to coastal resource managers for identifying areas in their jurisdiction where SGD may be a confounding process. (LOICZ is a core project of the International Geosphere/Biosphere Programme.) Of the hundreds of globally distributed parameters in the LOICZ typology, a SGD subset of potentially relevant parameters may be culled. A quantitative combination of the relevant hydrological parameters can serve as a proxy for the SGD conditions not directly measured. Web-LOICZ View, geospatial software then provides an automated approach to clustering these data into groups of locations that have similar characteristics. It permits selection of variables, of the number of clusters desired, and of the clustering criteria, and provides means of testing predictive results against independent variables. Information on the occurrence of a variety of SGD indicators can then be incorporated into regional clustering analysis. With such tools, coastal managers can focus attention on the most likely sites of SGD in their jurisdiction and design the necessary measurement and modeling programs needed for integrated management.     

Removal of Toxoplasma gondii Oocysts from Sea Water by Eastern Oysters (Crassostrea virginica)

SUMMARY. Toxoplasma gondii infections have been reported in a number of marine mammals. Presently it is not known how these animals acquire T. gondii from their aquatic environment. The eastern oyster, Crassostrea virginica , has been shown to remove Cryptosporidium oocysts from seawater and a similar phenomenon may be occurring with T. gondii oocysts and marine invertebrates. The present study was done to determine if eastern oysters could remove and retain T. gondii oocysts from seawater. Oocysts of the VEG strain of T. gondii (1 × 10⁶ oocysts) were placed in seawater (32 ppt NaCl) containing live eastern oysters. The infected seawater was removed one day postinoculation (PI) and replaced with fresh seawater. Selected oysters were removed at 1, 3 and 6 days PL Hemolymph, gill washes, and oyster tissue were collected separately at each observation time. The oyster tissue was homogenized and all 3 samples fed separately to mice. Toxoplasma gondii positive mice were observed at each time period. The results indicate that T. gondii oocysts can be removed from seawater by eastern oysters and retain their infectivity. Contaminated raw oysters may serve as a source of T. gondii infection for marine mammals and humans.     

Meta-Analysis of Quantification Methods Shows that Archaea and Bacteria Have Similar Abundances in the Subseafloor

There is no universally accepted method to quantify bacteria and archaea in seawater and marine sediments, and different methods have produced conflicting results with the same samples. To identify best practices, we compiled data from 65 studies, plus our own measurements, in which bacteria and archaea were quantified with fluorescent in situ hybridization (FISH), catalyzed reporter deposition FISH (CARD-FISH), polyribonucleotide FISH, or quantitative PCR (qPCR). To estimate efficiency, we defined “yield” to be the sum of bacteria and archaea counted by these techniques divided by the total number of cells. In seawater, the yield was high (median, 71%) and was similar for FISH, CARD-FISH, and polyribonucleotide FISH. In sediments, only measurements by CARD-FISH in which archaeal cells were permeabilized with proteinase K showed high yields (median, 84%). Therefore, the majority of cells in both environments appear to be alive, since they contain intact ribosomes. In sediments, the sum of bacterial and archaeal 16S rRNA gene qPCR counts was not closely related to cell counts, even after accounting for variations in copy numbers per genome. However, qPCR measurements were precise relative to other qPCR measurements made on the same samples. qPCR is therefore a reliable relative quantification method. Inconsistent results for the relative abundance of bacteria versus archaea in deep subsurface sediments were resolved by the removal of CARD-FISH measurements in which lysozyme was used to permeabilize archaeal cells and qPCR measurements which used ARCH516 as an archaeal primer or TaqMan probe. Data from best-practice methods showed that archaea and bacteria decreased as the depth in seawater and marine sediments increased, although archaea decreased more slowly.     

Effects of fresh and seawater ingestion on osmoregulation in Atlantic bottlenose dolphins (Tursiops truncatus)

Bottlenose dolphins (Tursiops truncatus) are marine mammals with body water needs challenged by little access to fresh water and constant exposure to salt water. Osmoregulation has been studied in marine mammals for a century. Research assessing the effects of ingested fresh water or seawater in dolphins, however, has been limited to few animals and sampling times. Nine 16- to 25-h studies were conducted on eight adult dolphins to assess the hourly impact of fresh water, seawater, and seawater with protein ingestion on plasma and urine osmolality, urine flow rate (ufr), urinary and plasma solute concentrations, and solute clearance rates. Fresh water ingestion increased ufr. Fresh water ingestion also decreased plasma and urine osmolality, sodium and chloride urine concentrations, and solute excretion rates. Seawater ingestion resulted in increased ufr, sodium, chloride, and potassium urine concentrations, sodium excretion rates, and urine osmolality. Seawater with protein ingestion was associated with increased ufr, plasma osmolality, sodium excretion, and sodium, chloride, potassium, and urea urine concentrations. In conclusion, bottlenose dolphins appear to maintain water and plasma solute balance after ingesting fresh water or seawater by altering urine osmolality and solute clearance. Ingestion of protein with seawater appears to further push osmoregulation limits and urine solute concentrations in dolphins.     

The survivability of the ectoparasitic flagellate Ichthyobodo necator on chum salmon fry (Oncorhynchus keta) in seawater and comparison to Ichthyobodo sp. on Japanese flounder (Paralichthys olivaceus)

Experimental studies revealed that a freshwater ectoparasitic flagellate Ichthyobodo necator (Henneguy, 1883) could survive and reproduce in seawater after infected chum salmon fry, Oncorhynchus keta (Walbaum), were transferred directly from fresh water to 33% seawater. Minor morphological changes (slight reduction in body width, loss of twistlike wrinkles on body surface, and reduction in contractile vacuoles) were observed in the attached form of I. necator following transfer to seawater. The field survey also confirmed that I. necator occurs on chum salmon fry in seawater estuaries (salinity 17-34%) and in freshwater habitats. It was assumed that I. necator acquired salinity tolerance as a result of adapting to the migratory behavior of its anadromous host. Two morphologically similar bodonids, I. necator from chum salmon and Ichthyobodo sp. from marine Japanese flounder, Paralichthys olivaceus (Temminck and Schlegel), were differentiated by cross-infection experiments. Thus, the parasite from marine flounder should be regarded as a separate species from I. necator.     

The importance of culturing bacterioplankton in the 'omics' age

Progress in the culturing of microorganisms that are important to ocean ecology has recently accelerated, and technology has been a factor in these advances. However, rather than a single technological breakthrough, a combination of methods now enable microbiologists to screen large numbers of cultures and manipulate cells that are growing at the low biomass densities that are characteristic of those found in seawater. The value of ribosomal RNA databases has been reaffirmed, as they provide nucleic-acid probes for screening to identify important new species in culture. The new cultivation approaches have focused on specific targets that ecological studies suggest are significant for geochemical transformations, such as SAR11. Here, we review how to cultivate marine oligotrophs and why it is worth the effort.     

Impact of Submarine Groundwater Discharge on Marine Water Quality and Reef Biota of Maui

Generally unseen and infrequently measured, submarine groundwater discharge (SGD) can transport potentially large loads of nutrients and other land-based contaminants to coastal ecosystems. To examine this linkage we employed algal bioassays, benthic community analysis, and geochemical methods to examine water quality and community parameters of nearshore reefs adjacent to a variety of potential, land-based nutrient sources on Maui. Three common reef algae, Acanthophora spicifera, Hypnea musciformis, and Ulva spp. were collected and/or deployed at six locations with SGD. Algal tissue nitrogen (N) parameters (δ¹⁵N, N %, and C:N) were compared with nutrient and δ¹⁵N-nitrate values of coastal groundwater and nearshore surface water at all locations. Benthic community composition was estimated for ten 10-m transects per location. Reefs adjacent to sugarcane farms had the greatest abundance of macroalgae, low species diversity, and the highest concentrations of N in algal tissues, coastal groundwater, and marine surface waters compared to locations with low anthropogenic impact. Based on δ¹⁵N values of algal tissues, we estimate ca. 0.31 km² of Kahului Bay is impacted by effluent injected underground at the Kahului Wastewater Reclamation Facility (WRF); this region is barren of corals and almost entirely dominated by colonial zoanthids. Significant correlations among parameters of algal tissue N with adjacent surface and coastal groundwater N indicate that these bioassays provided a useful measure of nutrient source and loading. A conceptual model that uses Ulva spp. tissue δ¹⁵N and N % to identify potential N source(s) and relative N loading is proposed for Hawaiʻi. These results indicate that SGD can be a significant transport pathway for land-based nutrients with important biogeochemical and ecological implications in tropical, oceanic islands.     

Successful information exchange between restoration science and practice

The science‐practice gap is often cited as a limitation to successful restoration outcomes; however, the existence of such a gap in information exchange is rarely measured. Here, we quantify the gap by focusing on common recommendations from both scientists (i.e. researchers) and managers (i.e. practitioners, land managers) on what is needed for successful restoration. We surveyed 45 managers associated with 244 invasive species (Tamarix spp.) removal projects across the southwestern U.S. to determine the degree to which they have utilized four strategies advocated by scientists: (1) collaborate widely, (2) monitor beyond cursory visual methods, (3) use a variety of information sources, and (4) consider project goals beyond invasive species removal. Half of these managers were also interviewed to assess managers' perceptions of the role of science in restoration. Twenty‐three scientists specializing in Tamarix‐related research in this region were also surveyed to assess how much they understood and/or shared the concerns of land managers. We found that managers were following scientists' recommendations and that managers' perceptions of the role of science in land management did not have any bearing on the management actions taken. Scientists reported being influenced by managers, and the concerns of scientists and managers were more overlapping than expected. Boundary organizations and river‐wide partnerships were often cited as important in facilitating effective communication between land managers and scientists. A lack of funding for monitoring and for longer‐term projects was cited by both groups as a limitation to incorporating scientists' recommendations into restoration.     

Zonation, behaviour and morphology of the intertida coral-treader Hermatobates (Hemiptera: Hermatobatidae) in the south-exst Pacific

The coral-treaders (Hermatobatidae) are the only exclusively marine family of insects. Observations in the Cook Islands, Samoa, Tonga and Fiji show that the insects can be abundant on shores that provide rocks with cavities that remain air-filled during high tide. The zone of suitable habitats for the insects is restricted to a narrow ( c. 20 cm) vertical band roughly centred around Mean Low Water Neaps. Transplant experiments show that the insects are unable to survive above or below this zone. The insects emerge from their rocky crevices about an hour before low tide, swim on the water surface during low tide, and return to their crevices about an hour after the tide has turned. There are only four larval instars, which can be readily separated by their morphology. Electron microscope studies show that the insects are clothed in a layer of micro-hairs of unique design: a short tapering shaft tipped with a sphere. These micro-hairs may act as a plastron: their distribution corresponds precisely to the pattern of the silvery 'air-layer' seen when the insects are submerged, their spherical tips provide a regular array that could support an air-water interface, they occur at high densities (up to 3.5 times 10⁶ mm^-2), and the layer makes connection with the thoracic spiracles. Half the insects were able to survive submergence in recirculated seawater for 12 hours. The adults appear to swim further from shore than the larvae, and they were observed copulating in tidal pools.     

Spatial confusion or clarity? Reply to Ricotta & Avena

Abstract. This communication is a response to a recent suggestion that ordinal data of the Braun‐Blanquet type (BB) can be directly or, after conversion to ranks, indirectly analysed by metric methods. I show that the proposals on structure in topological spaces made by Ricotta & Avena in a recent contribution to this Forum are confounding because (1) they use the term ‘topological’ in the inappropriate way, and (2) the measure they propose is in fact a metric, rather than merely topological. In addition, I illustrate with a few examples how a truly topological measure functions, so that the reader can appreciate the ideas behind their definitions. By reference to axiomatic measurement theory, I argue that whenever vegetation scientists know exactly at the outset what attributes they wish to express by relevé data, what questions they are asking and whenever they are aware of the basic properties of the BB scale, ordinal data analysis is still the most logical choice.     

Native marine bacteriophages

Abstract Isolation and cultivation of marine bacteriophages have shown that they are ubiquitous in seawater, and direct counting has shown that the total numbers of viruses frequently exceed the bacterial concentration by a factor of 10. About 150 different isolates of phages from marine environments have been characterized in the literature reviewed in the present report. Knoblike projections on phage heads seem to be a morphological property more common in marine phages than among phages from other sources. The cultured phages were generally much larger than the majority of viruses observed by direct transmission electron microscopy of seawater samples, indicating that culturing methods are not providing unbiased samples of environmental viruses. Cultured marine viruses frequently are more sensitive to organic solvents than the more intensively studied phages from other sources. Burst sizes from recent in situ studies are 50% lower than the average from culture studies. Phages in the marine environment may have half lives lasting less than a day, with consequent high turnover. Host ranges varies, and cross species host ranges have not been demonstrated. More information and further development of methods are needed, both from culture and from in situ studies.