Shallow Coastal Environments Research Articles

海洋健全度を用いた沿岸環境の定量的評価手法の提案

Valuing coastal ecosystem service is important for disentangling the complex human society-ecosystem relationships and incorporating the value into public decision-making processes. We developed a new evaluation method to comprehensively and concisely quantify the current status and likely future of shallow coastal environments by an ocean health index (OHI) score. We evaluated the environmental condition of four intertidal flats located in Tokyo Bay using OHI. Our method can provide a tool to explicitly show the strengths and limitations of each coastal ecosystem functioning.

Sediment flux modeling: Calibration and application for coastal systems

Benthic–pelagic coupling in shallow estuarine and coastal environments is an important mode of particle and solute exchange and can influence lag times in the recovery of eutrophic ecosystems. Links between the water column and sediments are mediated by particulate organic matter (POM) deposition to the sediment and its subsequent decomposition. Some fraction of the regenerated nutrients are returned to the water column. A critical component in modeling sediment fluxes is the organic matter flux to the sediment. A method is presented for estimating POM deposition, which is especially difficult to measure, by using a combination of long term time series of measured inorganic nutrient fluxes and a mechanistic sediment flux model (SFM). A Hooke–Jeeves pattern search algorithm is used to adjust organic matter deposition to fit ammonium (NH4+) flux at 12 stations in Chesapeake Bay for up to 17 years.POM deposition estimates matched reasonably well with sediment trap estimates on average (within 10%) and were strongly correlated with previously published estimates based upon sediment chlorophyll-a (chl-a) distribution and degradation. Model versus field data comparisons of NH4+ flux, sediment oxygen demand (SOD), sulfate (SO42−) reduction rate, porewater NH4+, and sedimentary labile carbon concentrations further validated model results and demonstrated that SFM is a powerful tool to analyze solute fluxes. Monthly model-field data comparisons clearly revealed that POM decomposition in the original SFM calibration was too rapid, which has implications for lagged ecosystem responses to nutrient management efforts. Finally, parameter adjustments have been made that significantly improve model-field data comparisons and underscore the importance of revisiting and recalibrating models as long time series (>5 years) become available.

SEMAT — The Next Generation of Inexpensive Marine Environmental Monitoring and Measurement Systems

There is an increasing need for environmental measurement systems to further science and thereby lead to improved policies for sustainable management. Marine environments are particularly hostile and extremely difficult for deploying sensitive measurement systems. As a consequence the need for data is greatest in marine environments, particularly in the developing economies/regions. Expense is typically the most significant limiting factor in the number of measurement systems that can be deployed, although technical complexity and the consequent high level of technical skill required for deployment and servicing runs a close second. This paper describes the Smart Environmental Monitoring and Analysis Technologies (SEMAT) project and the present development of the SEMAT technology. SEMAT is a “smart” wireless sensor network that uses a commodity-based approach for selecting technologies most appropriate to the scientifically driven marine research and monitoring domain/field. This approach allows for significantly cheaper environmental observation systems that cover a larger geographical area and can therefore collect more representative data. We describe SEMAT's goals, which include: (1) The ability to adapt and evolve; (2) Underwater wireless communications; (3) Short-range wireless power transmission; (4) Plug and play components; (5) Minimal deployment expertise; (6) Near real-time analysis tools; and (7) Intelligent sensors. This paper illustrates how the capacity of the system has been improved over three iterations towards realising these goals. The result is an inexpensive and flexible system that is ideal for short-term deployments in shallow coastal and other aquatic environments.

Formal analysis and evaluation of allometric methods for estimating above-ground biomass of eelgrass

Eelgrass (Zostera marina) populations supply substantial amounts of organic materials to food webs in shallow coastal environments, provide habitat for many fishes and their larvae and abate erosion. The characterisation of eelgrass biomass dynamics is an important input for the assessment of the function and values for this important seagrass species. We here present original allometric methods for the non-destructive estimation of above-ground biomass of eelgrass. These assessments are based on measurements of lengths and areas of leaves and sheaths and mathematical models that can be identified by means of standard regression procedures. The models were validated by using data obtained from Z. marina meadows in the Punta Banda estuary B.C., Mexico, and in Jindong Bay, Korea. Using available data and concordance correlation index criteria we show that the values projected thorough the presented allometric paradigm reproduces observed values in a consistent way. The annual average value for observed above-ground biomass was 1.46 ± 0.15 g shoot−1, while the corresponding calculated value was 1.40 ± 0.13 g shoot−1. We suggest that our method can be applied to other studies in which the architecture and growth form of leaves and sheaths are similar to those of eelgrass. This would provide reliable and simplified estimations of biomass while eliminating tedious laboratory processing and avoiding destructive sampling.

Pleistocene isolation, secondary introgression and restricted contemporary gene flow in the pig-eye shark, Carcharhinus amboinensis across northern Australia

We examine the structure and phylogeography of the pig-eye shark (Carcharhinus amboinensis) common in shallow coastal environments in northern Australia using two types of genetic markers, two mitochondrial (control region and NADH hydrogenase 4) and two nuclear (microsatellite and Rag 1) DNA. Two populations were defined within northern Australia on the basis of mitochondrial DNA evidence, but this result was not supported by nuclear microsatellite or Rag 1 markers. One possibility for this structure might be sex-specific behaviours such as female philopatry, although we argue it is doubtful that sufficient time has elapsed for any potential signatures from this behaviour to be expressed in nuclear markers. It is more likely that the observed pattern represents ancient populations repeatedly isolated and connected during episodic sea level changes during the Pleistocene epoch, until current day with restricted contemporary gene flow maintaining population genetic structure. Our results show the need for an understanding of both the history and ecology of a species in order to interpret patterns in genetic structure.

Assessment of pH variability at a coastal CO 2 vent for ocean acidification studies

Marine environments with naturally high CO 2 concentrations have become important research sites for studying the impacts of future ocean acidification on biological processes. We conducted high temporal resolution pH and temperature measurements in and around a shallow (2.5–3 m) CO 2 vent site off Ischia, Italy in May and June 2008. Loggers were deployed at five stations to monitor water at both the surface and benthos. Our reference station, 500 m from the CO 2 vent, had no noticeable vent influence. It had a naturally high and stable benthic pH (mean 8.16, inter-quartile range (IQ): 8.14–8.18) fluctuating with diel periodicity, presumably driven by community photosynthesis and respiration. A principal component analysis (PCA) revealed that the pH of this station was well constrained by meteorological parameters. In contrast, a station positioned within the vent zone, had a low and very variable benthic mean pH of 7.11 (IQ: 6.91–7.62) with large pH fluctuations not well constrained by a PCA. Any stations positioned within 20 m of the main vent zone had lowered pH, but suffered from abnormally large pH fluctuations making them unsuitable representatives to predict future changes to a shallow coastal environment. Between these extremes, we identified a benthic area with a lower pH of 7.84 (IQ: 7.83–7.88) that retained many of the characteristics of the reference station such as a natural diel pH periodicity and low variability. Our results indicate that a range of pH environments maybe commonplace near CO 2 vents due to their characteristic acidification of benthic water over a wide area. Such environments could become invaluable natural laboratories for ocean acidification research, closely mimicking future CO 2 conditions in a natural setting.

Stratigraphy of the Cenomanian–Turonian Oceanic Anoxic Event OAE2 in shallow shelf sequences of NE Egypt

Two shallow water late Cenomanian to early Turonian sequences of NE Egypt have been investigated to evaluate the response to OAE2. Age control based on calcareous nannoplankton, planktic foraminifera and ammonite biostratigraphies integrated with δ 13C stratigraphy is relatively good despite low diversity and sporadic occurrences. Planktic and benthic foraminiferal faunas are characterized by dysoxic, brackish and mesotrophic conditions, as indicated by low species diversity, low oxygen and low salinity tolerant planktic and benthic species, along with oyster-rich limestone layers. In these subtidal to inner neritic environments the OAE2 δ 13C excursion appears comparable and coeval to that of open marine environments. However, in contrast to open marine environments where anoxic conditions begin after the first δ 13C peak and end at or near the Cenomanian–Turonian boundary, in shallow coastal environments anoxic conditions do not appear until the early Turonian. This delay in anoxia appears to be related to the sea-level transgression that reached its maximum in the early Turonian, as observed in shallow water sections from Egypt to Morocco.

Integrating Quickbird Multi-Spectral Satellite and Field Data: Mapping Bathymetry, Seagrass Cover, Seagrass Species and Change in Moreton Bay, Australia in 2004 and 2007

Shallow coastal ecosystems are the interface between the terrestrial and marine environment. The physical and biological composition and distribution of benthic habitats within these ecosystems determines their contribution to ecosystem services and biodiversity as well as their connections to neighbouring terrestrial and marine ecosystem processes. The capacity to accurately and consistently map and monitor these benthic habitats is critical to developing and implementing management applications. This paper presents a method for integrating field survey data and high spatial resolution, multi-spectral satellite image data to map bathymetry and seagrass in shallow coastal waters. Using Quickbird 2 satellite images from 2004 and 2007, acoustic field survey data were used to map bathymetry using a linear and ratio algorithm method; benthic survey field data were used to calibrate and validate classifications of seagrass percentage cover and seagrass species composition; and a change detection analysis of seagrass cover was performed. The bathymetry mapping showed that only the linear algorithm could effectively and accurately predict water depth; overall benthic map accuracies ranged from 57–95%; and the change detection produced a reliable change map and showed a net decrease in seagrass cover levels, but the majority of the study area showed no change in seagrass cover level. This study demonstrates that multiple spatial products (bathymetry, seagrass and change maps) can be produced from single satellite images and a concurrent field survey dataset. Moreover, the products were produced at higher spatial resolution and accuracy levels than previous studies in Moreton Bay. The methods are developed from previous work in the study area and are continuing to be implemented, as well as being developed to be repeatable in similar shallow coastal water environments.

Sediment and Lower Water Column Oxygen Consumption in the Seasonally Hypoxic Region of the Louisiana Continental Shelf

We report integrated measurements of sediment oxygen consumption (SOC) and bottom water plankton community respiration rates (WR) during eight cruises from 2003 to 2007 on the Louisiana continental shelf (LCS) where hypoxia develops annually. Averaged by cruise, SOC ranged from 3.9 to 25.8 mmol O2 m−2 day−1, whereas WR ranged from 4.1 to 10.8 mmol O2 m−3 day−1. Total below-pycnocline respiration rates ranged from 46.4 to 104.5 mmol O2 m−2 day−1. In general, below-pycnocline respiration showed low variability over a large geographic and temporal range, and exhibited no clear spatial or inter-annual patterns. SOC was strongly limited by dissolved oxygen (DO) in the overlying water; whereas, WR was insensitive to low DO, a relationship that may be useful for parameterizing future models. The component measures, WR and SOC, were similar to most prior measurements, both from the LCS and from other shallow estuarine and coastal environments. The contribution of SOC to total below-pycnocline respiration averaged 20 ± 4%, a finding that differs from several prior LCS studies, but one that was well supported from the broader estuarine and oceanic literature. The data reported here add substantially to those available for the LCS, thus helping to better understand oxygen dynamics on the LCS.

Morphological variation of Thalassia testudinum in two shallow coastal environments from the southeastern Gulf of Mexico

Total biomass, shoot density, leaf length and leaf width of the dominant seagrass Thalassia testudinum were compared between two coastal environments in the northeastern part of the Yucatan peninsula (Mexico). The coastal environments were (a) an exposed sublittoral zone (<1 km from the shoreline) and (b) a sheltered coastal lagoon. Plant morphology was monitored at monthly intervals from June 2001 to May 2002. There was a clear morphological variation between coastal environments throughout the period of study. In the exposed sublittoral zone, total biomass and shoot density were lower and leaves were longer and wider. In contrast, in the sheltered lagoon, total biomass and shoot density were higher and the leaves shorter and narrower. Overall, high values of total biomass, shoot density and leaf width were observed during the warm weather seasons (rainy and dry) whereas the low values were observed during the cold fronts weather season (nortes); leaf length followed a reverse trend. Results presented here stress the need to take into account the natural pattern of morphological variation in the design of sampling and monitoring programs.

Hydrological heterogeneity, nutrient dynamics and water quality of a non-tidal lentic ecosystem (Lesina Lagoon, Italy)

The dynamics of the Lesina coastal lagoon (Italy) in terms of nutrients, phytoplankton and chemical–physical parameters were evaluated, together with their functional relationships with freshwater inputs, in order to identify ecosystem responses to changes in driving forces in a Mediterranean non-tidal lentic environment. Lesina Lagoon is a shallow coastal environment characterised by limited exchange with coastal waters, which favours enrichment of nutrients and organic matter and benthic fluxes within the system. Lagoon–sea exchanges are influenced by human management. There is a steep salinity gradient from East to West. High nitrogen and silica values were found close to freshwater inputs, indicating wastewater discharges and agricultural runoff, especially in winter. Dissolved oxygen was well below saturation (65%) near sewage and runoff inputs in the western part of the lagoon during summer. Classification in accordance with EEA (2001) guidelines suggests the system is of “poor” or “bad” quality in terms of nitrogen concentrations in the eastern zone during the winter rainy period. In terms of phosphate concentrations, the majority of the stations fall into the “good” category, with only two stations (close to the sewage and runoff inputs) classed as “bad”. In both cases, the raw nitrogen levels make the lagoon a P-limited system, especially in the eastern part. There was wide space–time variability in chlorophyll a concentrations, which ranged from 0.25 to 56 μg l −1. No relationships between chlorophyll a and nutrients were found, suggesting that autotrophic biomass may be controlled by a large number of internal and external forcing factors driving eutrophication processes. Water quality for this type of environment depends heavily on pressure from human activities but also on the management of sewage treatment plants, agricultural practices and the channels connecting the lagoon with the sea.

210Pb-derived ages for the reconstruction of terrestrial contaminant history into the Mexican Pacific coast: Potential and limitations

210Pb is widely used for dating recent sediments in the aquatic environment; however, our experiences working in shallow coastal environments in the Pacific coast of Mexico have demonstrated that the potential of 210Pb for reliable historical reconstructions might be limited by the low 210Pb atmospheric fallout, sediment mixing, abundance of coarse sediments and the lack of 137Cs signal for 210Pb corroboration. This work discusses the difficulties in obtaining adequate sedimentary records for geochronological reconstruction in such active and complex settings, including examples of 210Pb geochronologies based on sediment profiles collected in two contrasting areas coastal areas (mudflats associated to coastal lagoons of Sinaloa State and the continental shelf of the Gulf of Tehuantepec), in which geochemical data was used to support the temporal frame established and the changes in sediment supply recorded in the sediment cores which were related to the development of land-based activities during the last century.

Ultraviolet radiation induces structural and chromatin damage in Mediterranean sea-urchin spermatozoa

There is growing concern about the effects of enhanced levels of solar ultraviolet radiation on the living components of the biosphere (i.e. cancer, loss of biodiversity and productivity, etc.). In shallow coastal environments, many benthic species release their gametes directly in the water column where fertilisation occurs and the planktonic larvae remain for several weeks. Any effects on these early life stages could significantly impair reproductive input or alter the fitness of the community. The purpose of this paper is to provide new insights into the mechanisms of UV toxicity on sea-urchin spermatozoa in a cytological context, and to address the question of the potential ecological consequences of the damage. The Mediterranean sea-urchin Sphaerechinus granularis (Lamarck) was chosen as a model to study the effects of ecologically relevant doses of UV-R on the spermatozoa of marine invertebrates. Structural damage was visualised by use of transmission electron microscopy and the single-cell gel electrophoresis (Comet) assay was used to assess chromatin integrity in spermatozoa. The present results provide experimental evidence that irradiation with UV induces structural and chromatin damage in sea-urchin sperm. Almost 90% of spermatozoa exhibited morphological alterations and DNA strand breakage increased 2-fold. The observed alterations of the acrosome, plasma membrane and mitochondria can explain the concomitant impairment of fertilisation (23% decrease of fertilisation rate), which in turn may affect reproductive success. On the other hand, how DNA damage and fertilisation rate correlate remains unclear; however, when not repaired genetic lesions can lead to abnormal development and/or the transmission of heritable damage. The 3-fold decrease of the frequency of 2-celled embryos indicates a delay or inhibition of the first cell division, which may be ascribed to impairment of nuclear chromatin and/or other cellular targets.

Regeneration of nitrogen (15N) from seagrass litter in tropical Indo-Pacific meadows

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 368:165-175 (2008) - DOI: https://doi.org/10.3354/meps07619 Regeneration of nitrogen (15N) from seagrass litter in tropical Indo-Pacific meadows Jan Arie Vonk1,2,*, Johan Stapel1,3 1Department of Environmental Science, Institute for Wetland and Water Research, Faculty of Science, Radboud University Nijmegen, PO Box 9010, 6500 GL Nijmegen, The Netherlands 2Present address: Laboratory of Environmental Risk Assessment, National Institute for Public Health and the Environment (RIVM), PO Box 1, 3720 BA Bilthoven, The Netherlands 3Present address: Royal Netherlands Academy of Arts and Sciences, PO Box 19121, 1000 GC Amsterdam, The Netherlands *Email: javonk@gmail.com ABSTRACT: The input of nitrogen (N) into litter of the seagrasses Thalassia hemprichii, Halodule uninervis and Cymodocea rotundata during decomposition and the uptake of N released from this litter by the surrounding seagrasses were examined simultaneously using 15N-enriched seagrass leaf material (δ15N ≈ 500‰) placed in litterbags in seagrass meadows. The biomass (dry weight) decomposition rates (k) for these tropical seagrasses were high (0.023 to 0.070 d–1). Litter N concentration declined during decomposition, indicating an overall release of N during decomposition. Besides release of litter N there was an input of non-litter N, indicated by a decline of δ15N values. This exogenous N made up an important part of litter N, consisting of ca. 25% of the total standing stock litter N. The increased δ15N values of the surrounding seagrasses were used to calculate the uptake of N released from the macrophyte litter. The seagrasses efficiently took up the released N. The canopy thickness (aboveground biomass) of the seagrass meadow played a role in the uptake efficiency of N released from litter, increasing the N retention in these tropical meadows. The high litter decomposition rates, substantial input of exogenous N onto litter and efficient uptake of N released from litter suggest that N cycling, outside the living plant but within the meadow via the detrital pathway, is important to retain N in these nutrient-poor tropical meadows, despite the open and highly dynamic shallow coastal environments from which an easy loss of N, either dissolved in the water column or associated with the export of leaf litter, would be expected. KEY WORDS: Nitrogen cycling · Tropical seagrass · Uptake · Decomposition · 15N Full text in pdf format PreviousNextCite this article as: Vonk JA, Stapel J (2008) Regeneration of nitrogen (15N) from seagrass litter in tropical Indo-Pacific meadows. Mar Ecol Prog Ser 368:165-175. https://doi.org/10.3354/meps07619 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 368. Online publication date: September 25, 2008 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2008 Inter-Research.

Light-Dependant Biostabilisation of Sediments by Stromatolite Assemblages

For the first time we have investigated the natural ecosystem engineering capacity of stromatolitic microbial assemblages. Stromatolites are laminated sedimentary structures formed by microbial activity and are considered to have dominated the shallows of the Precambrian oceans. Their fossilised remains are the most ancient unambiguous record of early life on earth. Stromatolites can therefore be considered as the first recognisable ecosystems on the planet. However, while many discussions have taken place over their structure and form, we have very little information on their functional ecology and how such assemblages persisted despite strong eternal forcing from wind and waves. The capture and binding of sediment is clearly a critical feature for the formation and persistence of stromatolite assemblages. Here, we investigated the ecosystem engineering capacity of stromatolitic microbial assemblages with respect to their ability to stabilise sediment using material from one of the few remaining living stromatolite systems (Highborne Cay, Bahamas). It was shown that the most effective assemblages could produce a rapid (12–24 h) and significant increase in sediment stability that continued in a linear fashion over the period of the experimentation (228 h). Importantly, it was also found that light was required for the assemblages to produce this stabilisation effect and that removal of assemblage into darkness could lead to a partial reversal of the stabilisation. This was attributed to the breakdown of extracellular polymeric substances under anaerobic conditions. These data were supported by microelectrode profiling of oxygen and calcium. The structure of the assemblages as they formed was visualised by low-temperature scanning electron microscopy and confocal laser microscopy. These results have implications for the understanding of early stromatolite development and highlight the potential importance of the evolution of photosynthesis in the mat forming process. The evolution of photosynthesis may have provided an important advance for the niche construction activity of microbial systems and the formation and persistence of the stromatolites which came to dominate shallow coastal environments for 80% of the biotic history of the earth.

Spatial distribution of sedimentary linear alkylbenzenes and faecal steroids of Santos Bay and adjoining continental shelf, SW Atlantic, Brazil: Origin and fate of sewage contamination in the shallow coastal environment

Spatial distribution of sedimentary linear alkylbenzenes and faecal steroids of Santos Bay and adjoining continental shelf, SW Atlantic, Brazil: Origin and fate of sewage contamination in the shallow coastal environment

Medium-term effects of die-off of rocky benthos in the Ligurian Sea. What can we learn from gorgonians?

Mediterranean Sea ecosystems are experiencing a phase of major modifications owing to the fast increase in several disturbances such as pollution, eutrophication, habitat destruction, over-fishing, income of alien species, and climate change. One of the main problems in recent years is that global warming seems to intensify the effects of all the above-mentioned disturbances, dramatically reducing the biodiversity of the basin. The ever more frequent mass mortalities that are affecting shallow coastal environments are rapidly reducing the biomass of several filter feeders and both sponges and gorgonians are the most endangered taxa. In this paper we review the most recent episodes of mass mortality, mainly involving sea fans, and discuss the possible effects that the loss of these organisms can have on benthic assemblage structure. The data presented here are referred mainly to the study case of the MPA of Portofino (Ligurian Sea, Italy).

Nitrogen isotopic discrimination by water column nitrification in a shallow coastal environment

Temporal changes in nitrogen isotopic composition (δ15N) of the NO3 − pool in the water column below the pycnocline in Ise Bay, Japan were investigated to evaluate the effect of nitrification on the change in the δ15N in the water column. The δ15N of NO3 − in the lower layers varied from −8.5‰ in May to +8.4‰ in July in response to the development of seasonal hypoxia and conversion from NH4 + to NO3 −. The significantly 15N-depleted NO3 − in May most likely arose from nitrification in the water column. The calculated apparent isotopic discrimination for water column nitrification (ɛnit = δ15Nsubstrate − δ15Nproduct) was 24.5‰, which lies within the range of previous laboratory-based estimates. Though prominent deficits of NO3 − from hypoxic bottom waters due to denitrification were revealed in July, the isotopic discrimination of denitrification in the sediments was low (ɛdenit = ∼1‰). δ15NNO3 in the hypoxic lower layer mainly reflects the isotopic effect of water column nitrification, given that water column nitrification is not directly linked with sedimentary denitrification and the effect of sedimentary denitrification on the change in δ15NNO3 is relatively small.

Coral microbial communities, zooxanthellae and mucus along gradients of seawater depth and coastal pollution

The high incidence of coral disease in shallow coastal marine environments suggests seawater depth and coastal pollution have an impact on the microbial communities inhabiting healthy coral tissues. A study was undertaken to determine how bacterial communities inhabiting tissues of the coral Montastraea annularis change at 5 m, 10 m and 20 m water depth in varying proximity to the urban centre and seaport of Willemstad, Curaçao, Netherlands Antilles. Analyses of terminal restriction fragment length polymorphisms (TRFLP) of 16S rRNA gene sequences show significant differences in bacterial communities of polluted and control localities only at the shallowest seawater depth. Furthermore, distinct differences in bacterial communities were found with increasing water depth. Comparisons of TRFLP peaks with sequenced clone libraries indicate the black band disease cyanobacterium clone CD1C11 is common and most abundant on healthy corals in less than 10 m water depth. Similarly, sequences belonging to a previously unrecognized group of likely phototrophic bacteria, herein referred to as CAB-I, were also more common in shallow water. To assess the influence of environmental and physiologic factors on bacterial community structure, canonical correspondence analysis was performed using explanatory variables associated with: (i) light availability; (ii) seawater pollution; (iii) coral mucus composition; (iv) the community structure of symbiotic algae; and (v) the photosynthetic activity of symbiotic algae. Eleven per cent of the variation in bacterial communities was accounted for by covariation with these variables; the most important being photosynthetically active radiation (sunlight) and the coral uptake of sewage-derived compounds as recorded by the delta(15)N of coral tissue.

A LONG‐BODIED LIZARD FROM THE LOWER CRETACEOUS OF JAPAN

Abstract: Platynotan lizards underwent a dramatic Late Cretaceous radiation into marine habitats. Beginning with small‐bodied forms, the lineage culminated with the mosasaurs, large predatory lizards with a world‐wide distribution in the Santonian–Campanian. Moreover, the marine squamate radiations of the Cenomanian–Turonian are remarkable in having produced a range of long‐bodied, reduced‐limbed swimmers (dolichosaurs, adriosaurs, coniasaurs and limbed snakes) that seem to have thrived in the shallow coastal environments of the Western Tethys region. Until now, none of these long‐bodied aquatic squamates has been recorded prior to the Cenomanian, none has been recovered from a non‐marine locality and none is known from Asia. Here we describe a small, gracile, long‐bodied mosasauroid lizard from a swampy continental deposit in the Lower Cretaceous of Japan.