Shallow Marine Bay Research Articles

МОРСКОЕ ОСАДКОНАКОПЛЕНИЕ НА ПОБЕРЕЖЬЕ ЮГО-ЗАПАДНОЙ ОКРАИНЫ ПРИМОРЬЯ В СРЕДНЕМ ГОЛОЦЕНЕ

A comprehensive study of marine sediments deposited at the southwestern margin of Primorye (Khasan settlement area) allowed us to consider in detail the palaeogeography of the coast in the second half of the Atlantic period of the Holocene, about 6 500–6 000 yr BP / 7 400–6 800 cal BP. Sedimentation in marine environments began with the development of postglacial oceanic transgression around 6 500 yr BP / 7 400 cal BP. A shallow marine bay formed on the coastal accumulation plain, into which the Tumannaya (Tumangan) River, the largest in the Sea of Japan basin, flowed. Avalanche sedimentation proceeded in the bay at an average rate of 16–24 mm/year within the confines of the estuary. The final phase of sedimentation after 6 200 yr BP / 7 100 cal BP occurred at a time when the transgression of the sea slowed down and sea level reached its maximum height of +1 m in the coastal area. Multi-species broad-leaved oak-dominated forests mixed with thermophilic hornbeam species clearly indicate optimum climatic conditions in the territory adjacent to the coast. The marine sedimentation stopped around 6 000 yr BP / 6 800 cal BP to resume in the middle of the Sub-Atlantic period of the Holocene.

Progressive opening of a shallow-marine bay (Oliete Subbasin, Spain) and the record of possible eustatic fall events near the Barremian-Aptian boundary

In this paper, we analyse the upper Barremian-lowermost Aptian Alacón Formation (Oliete subbasin, Maestrazgo Basin) of Spain to understand the progressive opening of a shallow-marine bay found on the northeastern margin of Iberia. The succession consists of four transgressive-regressive sequences (S1S4) bounded by widespread unconformities caused by rapid base-level fall. The transgressive interval of each sequence is characterized by relatively high detrital input and fresh-water inflow that caused the demise of shallow-marine benthic communities. The regressive interval of each sequence triggered progressive regeneration of the benthic carbonate producers. Sequences 1 and 2 consist of lacustrine to restricted shallow-marine facies, followed by accumulations of the gryphaeid oyster Ceratostreon , with progressive colonization of the bay by marine benthic communities subjected to frequent salinity oscillations. Sequences 3 and 4 represent the stabilization of open-marine conditions in the bay with widespread development of high-energy bioclastic tidal dunes. The long-term transgression around the Barremian-Aptian boundary, which gave rise to the progressive flooding of the Oliete bay, was episodically interrupted by shorter-term episodes of abrupt base-level fall, with the eventual subaerial exposure of the entire bay at the end of the deposition of the Alacón Formation. Our data suggest that the observed sequence architecture was mostly controlled by climatic and eustatic sea-level oscillations, with local synsedimentary tectonics having a minor impact. Two major sea-level fall events responsible for the discontinuities found on top of sequences 3 and 4 are possibly correlated to the cooling episodes close to the Barremian-Aptian boundary and during the earliest Aptian (predating the OAE 1a) described in many other worldwide basins. • The progressive opening of a shallow marine bay in Iberia (W Tethys) is documented. • Four sequences register progressive paleogeographical and paleoecological changes. • Sequence boundaries are tentatively linked to major cooling events KBa5 and KAp1.

Early Pliocene marine transgression into the lower Colorado River valley, southwestern USA, by re-flooding of a former tidal strait

Abstract Marine straits and seaways are known to host a wide range of sedimentary processes and products, but the role of marine connections in the development of large river systems remains little studied. This study explores a hypothesis that shallow-marine waters flooded the lower Colorado River valley at c. 5 Ma along a fault-controlled former tidal strait, soon after the river was first integrated into the northern Gulf of California. The upper bioclastic member of the southern Bouse Formation provides a critical test of this hypothesis. The upper bioclastic member contains wave ripple-laminated bioclastic grainstone with minor red mudstone, pebbly grainstone with hummocky cross-stratification (HCS)-like stratification and symmetrical gravelly ripples, and calcareous-matrix conglomerate. Fossils include upward-branching segmented coralline-like red algae with no known modern relatives but confirmed as marine calcareous algae, echinoid spines, barnacles, shallow-marine foraminifers, clams, and serpulid worm tubes. These results provide evidence for deposition in a shallow-marine bay or estuary seaward of the transgressive backstepping Colorado River delta. Tsunamis generated by seismic and meteorological sources likely produced the HCS-like and wave-ripple cross-bedding in poorly-sorted gravelly grainstone. Marine waters inundated a former tidal strait within a fault-bounded tectonic lowland that connected the lower Colorado River to the Gulf of California. Delta backstepping and transgression resulted from a decrease in sediment output due to sediment trapping in upstream basins and relative sea-level rise produced by regional tectonic subsidence.

Liquefaction and re-liquefaction of sediments induced by uneven loading and glacigenic earthquakes: Implications of results from the Latvian Baltic Sea coast

Seven internally-deformed layers were recognised in the shallow marine bay sediments deposited during mid Marine Isotope Stage 2 along the Latvian Baltic Sea coast bluff at Baltmuiža. Detailed sedimentological analyses of these deformed layers indicate that liquefaction was responsible for the development of soft-sediment deformation structures (SSDS) including injection structures, load casts, flame structures and pseudonodules. Traces of both initial liquefaction and re-liquefaction were recognised within at least four of the seven layers with SSDS (two different generations of pseudonodules and injection structures, clastic injection pipes, disrupted load casts). This is a unique finding, as it is difficult to re-liquefy sediment affected by previous liquefaction due to the increased packing of grains and decreased hydration after initial liquefaction. Furthermore, all layers with SSDS are characterised by eroded tops, which indicate that deformation took place when these layers were at the contemporary surface of sedimentation. We suggest that the initial liquefaction of fluidised coastal sediments was caused by various triggers (uneven loading, glacigenic earthquake), while the re-liquefaction could be related to a single trigger of mid-Late Weichselian glacigenic earthquakes at the front of the advancing last Fennoscandian Ice Sheet. Our results show that despite compaction after liquefaction, sediment re-liquefaction caused by an allogenic trigger is still possible under favourable conditions, i.e., sediment anisotropy, cyclic loading, and preserved high water saturation. Our findings are also the first to demonstrate the sedimentological imprints of re-liquefaction.

Neolithic to modern period palaeogeographic transformations in southern Danube delta and their impact on human settlements in the Enisala-Babadag region

Archaeological data provide evidence of human inhabitation in the Danube Delta since the Early Neolithic with once flourishing human settlements such is the case of Enisala and Babadag settlements. Their remains dating back from Eneolithic (Enisala) or Iron Age (Babadag) or from their revivals in Antiquity and Medieval Age have been found on higher grounds (i.e. hillslope terrace) in the immediate vicinity of Babadag and Razelm lakes and of the reedmarsh developed in-between the lakes. The settlements benefited from their strategical position defined by the intersection of the terrestrial routes linking the northern and southern Dobrudja with the navigation ways to the Black Sea via a shallow but open lagoon prior to Antiquity and later, post 7th c. BC, via Dunavăț branch of the Danube that extended the southern delta by successive open-coast deltaic lobes formation (2600-1300 yrs BP).This study documents the landscape transformation of the region since Early Neolithic to the present, based on sedimentological, chronostratigraphic, mineralogical, geochemical, magnetometric, macro- and microfauna analyses which altogether led to the identification of main stages: i) high floodplain (before 8000 BP), ii) wetlands (8000-7500 yrs BP), iii) shallow marine bay (7500–6000/5500 yrs BP), iv) lagoon (5500-460 yrs BP) and v) reedmarsh (460 yrs BP – present). Each type of landscape that succeeded in the Enisala-Babadag region is described in relation with shoreline position, (ground)water depth and Danube Delta development. Additionally, the tectonic subsidence of the studied wetlands (0.5–0.8 mm/yr) was assessed and its effects on the landscape changes and long-term morphodynamics are discussed.

The Miocene Depositional Geological Evolution of Phu Khanh, Nam Con Son and Tu Chinh - Vung May Basins in Vietnam Continental Shelf

The geological development history of Miocene deposits in three sedimentary basins as Phu Khanh, Nam Con Son and Tu Chinh - Vung May is actually a depositional evolution in relation to sea level change and tectonic movement. The Miocene deposits in three basins were formed in three cycles corresponding to three depositional sequences: 1/ Early Miocene sequence: In this cycle, the tectonic setting of three basins is similar to one another, the terrain is less differentiated, the environment is mainly alluvial, coastal and shallow marine-bay. Topography of top Miocene surface was strongly deformed by the tectonic events such as compression, fault, fold that had created the rough relief and eroded unconformity surface. The product of erosion processes was supply of terrigenous depositional materials for early Miocene basins under the bay type. 2/ Middle Miocene sequence: The tectonic situation of three basins started changing. The basins were differentiated into 2 parts: The inner shelf with stable geological structure and dominated terrigenous deposits; The outer shelf was stronger subsidence the basin base topography was differentiated with the development of two sediment types: carbonate bearing terrigenous sediments and carbonate reefs. 3/ Late Miocene sequence: in this period the basins were differentiated into two distinct structural zones: the western zone with incline terrain, the dominated terrigenous sediments and the eastern zone with strong differentiated terrain, reef development they played the erosion zone role and supplied a large amount of biological clastic sediments to the shallow lagoons-bay.

Zechstein marine deposits in the Wleń Graben (North Sudetic Synclinorium, SW Poland) – new insights into the palaeogeography of the southern part of the Polish Zechstein Basin

This paper presents the results of sedimentological studies of Zechstein marine deposits occurring in the Wlen Graben, a tectonic unit located in the southeastern part of the North Sudetic Synclinorium (NSS; Western Sudetes, SW Poland). Owing to poor exposure, small thickness, and lack of palaeontological data, the stratigraphy and age of these rocks were determined solely on the basis of analogies with adjacent areas. New findings described here, including faunal remains (remains of bivalves, including Liebea sp.), geopetal structures, clastic fills of halite crystals, moulds and bioturbation, shed new light on the environmental interpretations of the Zechstein in this part of the NSS. It should be assumed that at least two types of deposit may be assigned to the marine Zechstein in the Wlen Graben area, namely sparitic and microsparitic dolomite (PZ3) and the overlying deposits of the heterolithic series (PZt). These deposits were formed during the late Zechstein transgression, when the study area was in the marginal southwesternmost part of a newly formed shallow-marine bay of the Polish Zechstein Basin. In the central part of the present-day Wlen Graben, a shallow-marine bay (lagoon?) was dominated by carbonate sedimentation. A north-dipping mud plain, periodically flooded by a shallow sea, occurred in the southern part of the area. The paper summarises the present state of research on Permian deposits in the Wlen Graben, the first comprehensive lithostratigraphic scheme is suggested, and a new concept of the palaeogeographic evolution of the area in the Early and Late Permian is proposed.

Seasonal variation of training, competition load and markers of wellness in an elite Gaelic football team

Constraining the timing of the postglacial transgression is of great significance to the origin of coastal wetlands distributed extensively in eastern China. The high-resolution chronological sequence from Xixi Wetland enabled us to explore interactions among the postglacial transgression, sedimentary response, and human activities in the surrounding Hangzhou Bay. Diversities of 12 ostracods, 24 foraminifera and remains of oyster shells, gastropods, testate amoebae, diatoms, and vascular plants are indicative of the sedimentary facies. Grain size variables together with microfaunal records revealed seven stages of sedimentary evolution since the middle Late Pleistocene: initial riverbed, first transgression event, floodplain, early lagoon, shallow marine bay, late lagoon, and final freshwater marsh. The Xixi Basin experienced two distinct transgression events and sea-level changes inferred from assemblages of ostracods and foraminifera. The first transgression event is a minor transgression related to the moderate intensity of Asian Monsoon and moderately high sea level during the early MIS 3. The second large-scale transgression event established the sedimentary pattern of the modern Xixi Basin. The finding of the transgression maximum in the early Holocene (about 11.0–7.0 cal ka BP) highlighted the problem of reliable time of high sea level, which is tightly related to the strong Asian Monsoon intensity and global rising sea level. Subsequent changes in the sedimentary environment played a key role on the Neolithic human activities around the Hangzhou Bay. The origin of the Xixi Wetland reflected the combined effects of a sand barrier and rising human activities since the middle Holocene.

Postglacial transgression maximum documented by the core sediments of Xixi Wetland, East China

Constraining the timing of the postglacial transgression is of great significance to the origin of coastal wetlands distributed extensively in eastern China. The high-resolution chronological sequence from Xixi Wetland enabled us to explore interactions among the postglacial transgression, sedimentary response, and human activities in the surrounding Hangzhou Bay. Diversities of 12 ostracods, 24 foraminifera and remains of oyster shells, gastropods, testate amoebae, diatoms, and vascular plants are indicative of the sedimentary facies. Grain size variables together with microfaunal records revealed seven stages of sedimentary evolution since the middle Late Pleistocene: initial riverbed, first transgression event, floodplain, early lagoon, shallow marine bay, late lagoon, and final freshwater marsh. The Xixi Basin experienced two distinct transgression events and sea-level changes inferred from assemblages of ostracods and foraminifera. The first transgression event is a minor transgression related to the moderate intensity of Asian Monsoon and moderately high sea level during the early MIS 3. The second large-scale transgression event established the sedimentary pattern of the modern Xixi Basin. The finding of the transgression maximum in the early Holocene (about 11.0–7.0 cal ka BP) highlighted the problem of reliable time of high sea level, which is tightly related to the strong Asian Monsoon intensity and global rising sea level. Subsequent changes in the sedimentary environment played a key role on the Neolithic human activities around the Hangzhou Bay. The origin of the Xixi Wetland reflected the combined effects of a sand barrier and rising human activities since the middle Holocene.

Evidences for a Paleocene marine incursion in southern Amazonia (Madre de Dios Sub-Andean Zone, Peru)

This article presents new biostratigraphic dating, facies analysis, organic geochemical data and Nd–Sr isotopic provenance from five outcrops of southern Amazonia (MD-85, MD-177 MD-184, MD-255 and MD-256) to document for the first time the presence of a shallow marine ingression in the Paleocene of southern Amazonia basin. The co-occurrence of a selachian assemblage encompassing Potobatis sp., Ouledia sp., and Pristidae indet. with the ostracod Protobuntonia sp. and the charophytes Peckichara cf. varians meridionalis, Platychara perlata, and Feistiella cf. gildemeisteri suggests a Paleocene age for the studied deposits (most likely Thanetian but potentially Danian). Fifteen facies have been recognized and have been grouped into three facies assemblages. Facies association A corresponds to the sedimentary filling of a tide-influenced meandering channel formed in the fluvial–tidal transition zone. Facies association B is related to more distal tidal-flats, little channelized tidal inlets and saltmarsh deposits. Facies association C corresponds to a stressed shallow marine environment such as a bay or a lagoon. The δ13CTOC value (−23.4‰) of MD-184 is enriched in 13C compared to the other samples suggesting the presence of substantial amounts of marine organic matter in MD-184. The δ13CTOC values of samples from other outcrops (−27.3 to −29.8‰) indicate a mixed organic matter origin, from terrestrial to brackish environments. The analyzed sediments have similar Nd–Sr isotopic compositions as those of the Cenozoic sediments of the Altiplano (εNd(0) values from −6.2 to −10.7 and 87Sr/86Sr compositions from 0.712024 to 0.719026) indicating a similar volcanic source. This multidisciplinary dataset documents the presence of a tide-dominated estuary sourced by the proto-Western Cordillera debouching into a shallow marine bay during Paleocene times. This transgression might be explained by subsidence created in response to the proto-Western Cordillera loading. Similar to Miocene marine incursions affecting the Pebas megawetland, Paleogene marine incursions in the Amazonian foreland basin associated with Andean uplift may have played a role in the Neotropical biodiversity dynamics in favoring biogeographical isolation and promoting allopatric speciation for terrestrial organisms.

Habitat modelling limitations – Puck Bay, Baltic Sea – a case study

The Natura 2000 sites and the Coastal Landscape Park in a shallow marine bay in the southern Baltic have been studied in detail for the distribution of benthic macroorganisms, species assemblages and seabed habitats. The relatively small Inner Puck Bay (104.8km2) is one of the most thoroughly investigated marine areas in the Baltic: research has been carried out there continuously for over 50years. Six physical parameters regarded as critically important for the marine benthos (depth, minimal temperature, maximum salinity, light, wave intensity and sediment type) were summarized on a GIS map showing unified patches of seabed and the near-bottom water conditions. The occurrence of uniform seabed forms is weakly correlated with the distributions of individual species or multi-species assemblages. This is partly explained by the characteristics of the local macrofauna, which is dominated by highly tolerant, eurytopic species with opportunistic strategies. The history and timing of the assemblage formation also explains this weak correlation. The distribution of assemblages formed by long-living, structural species (Zostera marina and other higher plants) shows the history of recovery following earlier disturbances. In the study area, these communities are still in the stage of recovery and recolonization, and their present distribution does not as yet match the distribution of the physical environmental conditions favourable to them. Our results show up the limitations of distribution modelling in coastal waters, where the history of anthropogenic disturbances can distort the picture of the present-day environmental control of biota distributions.

Piraeus, the ancient island of Athens: Evidence from Holocene sediments and historical archives

The famous Greek geographer Strabo wrote in the fi rst century A.D., that Piraeus was formerly an island and lay ‘over against’ the mainland, from which it got its name. To validate Strabo’s hypothesis, cartographic and historical data were compiled with multiproxy paleoenvironmental analyses and radiocarbon dating from a series of boreholes drilled in the Cephissus coastal plain, southwest of Athens, Greece. The results of this interdisciplinary geoarchaeological research demonstrate the reliability of Strabo’s text by revealing that Piraeus was indeed an island. In early Holocene time, the rocky hill of Piraeus was linked to the mainland of Attica. During the late to fi nal Neolithic Period (4850‐3450 B.C.), Piraeus became an island in a shallow marine bay, due to sea-level rise in the Holocene. Between 2850 and 1550 B.C., in the Early and Middle Bronze Age, Piraeus was separated from the mainland by a wide lagoon. In the fi fth century B.C., Themistocles, Cimon, and then Pericles connected Athens to Piraeus by building two “long walls” partly built on a residual coastal marsh called the Halipedon. This study reveals an impressive example of past landscape evolution.

Reconstruction of Mid-Holocene sedimentary environments in the central part of the Thessaloniki Plain (Greece), based on microfaunal identification, magnetic susceptibility and grain-size analyses

The study aims to estimate the relative contributions of the two drainage basins of the Aliakmon and Axios rivers which, since the Mid-Holocene, have been responsible for building the largest deltaic area in Greece. Sediments from five cores located in the central part of the Thessaloniki Plain have been studied for their environmental changes using paleontological and sedimentological methods. Chronostratigraphical evidence was obtained from 14C AMS dating of marine shells, peat and organic sediment samples. During the Holocene marine transgression, this large coastal plain was a shallow marine bay reaching approx. 35 km inland circa the 4th millennium BC, from which the sea subsequently regressed to the east. Around the middle of the 3rd millennium BC, strong fluvial deposition of Aliakmon, to the east, and of Axios, to the north, occurred and was responsible of a gradual change to lagoonal and limnic environmental conditions. Around the 5th Century BC, a freshwater lake occupied the westernmost part of the plain. Microfaunal identification, together with magnetic susceptibility measurements, and grain-size analysis reveal three main environments of sediment deposition that reflect combinations of both concentrated and dispersed sources of magnetic/source minerals. Using remote sensing and a combination of spectral bands (LANDSAT TM imagery), we identify former fluvial levees and a freshwater lake, and give a spatial interpretation of the rivers' influences in building this deltaic complex. The mechanisms of edification of the plain as well as the roles played by Aliakmon and Axios sedimentation are described.

Homing and Daytime Tidal Movements of Juvenile Snappers (Lutjanidae) between Shallow-Water Nursery Habitats in Zanzibar, Western Indian Ocean

We studied daily tidal movements of tagged juvenile Lutjanus fulviflamma and Lutjanus ehrenbergii between two adjacent habitats, a subtidal channel and shallow tidal notches in the fossil reef terrace, in a shallow marine bay on Zanzibar Island (Tanzania). Due to a large tidal range, the notches were dry at low-tide and were only accessible to the snappers at high-tide. Of the resighted individuals, 48% showed clear movement between the two habitats, orientated in a direction perpendicular to the tidal currents. Individuals resighted more than once showed site fidelity, indicating homing in both the channel and the notches. We suggest that a significant part of this population of juvenile snappers may move from a low-tide resting habitat to a high-tide resting habitat during the daytime, perhaps to avoid predation by larger predators that may enter the channel at high-tide.

Cosmopolitan Metapopulations of Free-Living Microbial Eukaryotes

Metapopulations of macroscopic organisms tend to be geographically restricted, but free-living protists and other microbial eukaryotes present a different picture. Here we show that most organisms smaller than 1 mm occur worldwide wherever their required habitats are realised. This is a consequence of ubiquitous dispersal driven by huge population sizes, and the consequently low probability of local extinction. Organisms larger than 10 mm are much less abundant, and rarely cosmopolitan. The supporting data, together with the discovery that the 1-10 mm size range accommodates a transition from cosmopolitan to regionally-restricted distribution, were derived from extensive inventories of eukaryotic species in a freshwater pond (1278 species), and a shallow marine bay (785 species). All accessible records were examined to establish the extent of global coverage by these species. Some groups of microbial eukaryotes are severely undersampled (e.g. naked amoebae; marine meiofauna in the southern hemisphere) but this fails to weaken evidence that metapopulations of microbial eukaryotes are cosmopolitan.

Heavy Metal Accumulation and Anthropogenic Impacts on Tolo Harbour, Hong Kong

The surficial sediments in Tolo Harbour, Hong Kong, lie at the extreme landward end of a highly indented shallow marine bay. During the late Pleistocene and early Holocene this was a confluence area for several rivers, with marine flooding taking place between 8000 and 6000 years. B.P. Anthropogenic contamination with Cu, Pb and Zn has resulted in a pollution gradient that suggests major inputs from the Tai Po area to the north-west of Tolo Harbour, with further contamination inputs being derived from Shatin to the south-west. Core data for these metals demonstrate an increasing contamination trend over the last few decades. Ni also increases within cores, but spatial trends are less distinct. Cr exhibits no spatial or temporal pattern and probably reflects natural lithospheric contributions only. Cd occurred at very low levels. Generally pollution problems are moderate rather than extreme, but the area faces increasing urban pressures.

Role of Bacteria in the Carbon and Nitrogen Flow between Water‐Column and Sediment in a Shallow Marine Bay (Bay of Piran, Northern Adriatic Sea)

Abstract. The interdependences between phytoplankton standing crop, bacterial biomass and the dissolved organic matter (DOM) pool in the water column were investigated and related to sediment parameters in a shallow marine bay (Bay of Piran, Northern Adriatic Sea) over an annual cycle. Bacterioplankton density varied between 1–10 × 105 cells ml‐1, with lowest density observed in March corresponding to the low Chi a concentrations during this period. Generation times as determined by dialysis incubations ranged between 4h (June) and 82 h (March). Mean bacterial secondary production rates during summer were about 40 mg C m‐1 d‐1 and 5mg C m‐3.d‐1 during winter. With a short time lag, DOM concentrations followed the fluctuation in Chi a.Sediment oxygen demand measurements revealed a mean mineralization rate of about 260 mg C m‐2 d‐1 during summer and 100–200 mg C m‐2 d‐1 in winter. Sediment bacterial density varied between 108 ‐ 109 cells g (sediment dry wt)‐1 in the top 5 cm sediment layer or, in terms of biomass, 4.3 g C m‐l during summer and 0.6 g C m‐2 during winter. Highest concentrations of DOM in pore waters were measured in September, coinciding with high rates of sediment oxygen demand.

Diversity and structure of epifaunal communities on mollusc valves, Buzzards Bay, Massachusetts

The diversity, homogeneity and population structure of epifauna living on dead bivalve shells in a shallow marine bay are examined. Twenty-eight shells of Mercenaria mercenaria were artificially emplaced on each of three different sediment types in Buzzards Bay, Massachusetts, for one year. Living faunas (53,000 individuals assignable to 106 species) and preservable faunas (16,000 individuals assignable to 25 species) which colonized these shells are compared. Living epifaunas demonstrate a moderately good fit to the Preston truncated lognormal distribution but deviate consistently from the MacArthur broken-stick model. Homogeneity and diversity of living faunas are greater on shells resting on coarse sediments. The rarefaction methodology overestimates faunal diversity in both living and preservable faunas. Preservable epifaunas posses a higher homogeneity but one which is generally parallel to that of the living communities from which they are derived. The diversity of preservable epifaunas does not reflect the diversity of the living faunas from which they are derived. Abundant species living on shells are more likely to possess preservable hard parts than are rare species. This is indicative of the evolutionary success of various protective devices in epibenthic communities exposed to predation and environmental vagaries.

Photoelectric Ecosystem

A natural, self-maintaining photoelectric cell, composed of a blue-green algal mat and bacteria as a layered ecosystem, was isolated from a shallow marine bay in Texas near Port Aransas. In daytime the open-circuit Potential across the ecological membrane was about 0.43 volt. The efficiency of conversion of light energy to organic potential energy before maintenance was 1.62 percent and to external electrical energy at optimum power loading was 0.016 percent, a flow analogous to a consumer population.