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Journal Articles: River Deltas and FaunasArticles : Geology | Ecosystems | Climate Change | Sea Level Rise | Fauna | Birds | Fish
Abramova, E. N. and V. A. Sokolova (1999). "On findings and life cycle of Limnocalanus johanseni Marsh, 1920 (Copepoda, Calanoida) over the Lena River delta." Zoologichesky Zhurnal 78(11): 1360-1363. A new species for the local fauna, Limnocalanus johanseni, was found in freshwater lake Sagastyr, in the northern part of the Lena River delta. The life cycle of the species in comparison with that in sympatric species Heterocope borealis was investigated. Amadi, A. A. (1990). "A Comparative Ecology of Estuaries in Nigeria." Hydrobiologia 208(1-2): 27-38. A bar-built estuary, a drowned river valley and two river delta estuaries were compared and contrasted to elucidate the impact of some abiotic factors, notably climate, salinity, and oxygen on the distribution of the aquatic fauna and flora. Salinity was recognizable as the key factor responsible for the population dynamics in these habitats. The mangrove community is characteristically zoned, but development and distribution of the trees is restricted in view of coastal geomorphic and hydrological processes to the western banks of the estuaries. The preponderance of marine fish species in estuaries was confirmed, although the wide salinity tolerance of some prolific-breeding Cichlidae from freshwater was noted. Forty-eight species of bony fishes were recorded in Lagos Lagoon, the Escravos, and Qua Ibo estuaries and classified by salinity tolerance into stenohaline and euryhaline marine species (66%), and freshwater species (34%). The same estuarine ichthyofauna were split into trophic groups: piscivores (46%), zooplankton feeders (10%), meiobenthos feeders (27%), and macrobenthos feeders (17%). Blais- Stevens, A. and R. T. Patterson (1998). "Environmental indicator potential of foraminifera from Saanich Inlet, Vancouver Island, British Columbia, Canada." Journal of Foraminiferal Research 28(3): 201-219. Foraminiferal biofacies identified in Saanich Inlet appear to be closely linked to a variety of environmental parameters, including water quality, Five biofacies are defined based on Q-mode cluster analysis and on faunal distribution profiles of foraminifera-bearing surface sediment samples. Biofacies 1 (Eggerella advena Biofacies), which occurs in near shore environments near two bays with densely populated shorelines, appears to have an affinity for areas contaminated by sewage outfall and septic system drainage. Biofacies 2 (Eggerella advena-Spiroplectammina biformis Biofacies) and 3 (Miliammina fusca Biofacies) characterize shallow, brackish waters, and are distributed in shallow bays adjacent to Biofacies 1, Biofacies 4 (Lobatula fletcheri Biofacies), the only biofacies dominated by a calcareous fauna, has been subdivided into two sub-biofacies: Sub-biofacies 4A (Stainforthia feylingi Sub-biofacies) and 4B (Buccella frigida Sub-biofacies). Sub-biofacies 4A occurs in deep water, low oxygen environments, whereas Sub-biofacies 4B characterizes shallow water, normal marine environments. The patchy distribution of Sub-biofacies 4B samples is probably due to vagaries of water circulation in the restricted basin, Biofacies 5 (Leptohalysis catella-Spiroplectammina biformis Biofacies) occupies a relatively deeper muddy environment with a high proportion of plant debris and probably relatively lower oxygen levels. Hence, the main environmental control defining the biofacies is water circulation (or lack thereof), which is influenced by the shape of the fiord (presence of the sill). Boeskorov, G. G. (2004). "The north of Eastern Siberia: Refuge of Mammoth fauna in the Holocene." Gondwana Research 7(2): 451-455. The global climate changings at the end of Pleistocene led to extinction of the typical representatives of Mammoth fauna-mammoth, woolly rhinoceros, wild horse, bison, muskox, cave lion, etc-on the huge territories of Northern Eurasia. Undoubtedly the Mammoth fauna underwent pressure from the Upper Paleolithic Man, whose hunting activity also could play the role in decreasing the number of mammoths and other representatives of megafauna (large mammals). Archaeological data testify that the typical representatives of Mammoth fauna were the Man's hunting objects only till the end of the Pleistocene. Their bone remains are not usually found on the settlements of Mesolithic Man. Formerly it was supposed that the megafauna of 'Mammoth complex' was extinct by the beginning of Holocene. Nevertheless the latest data testify that the global extinction of the Mammoth fauna was sufficiently delayed in the north of Eastern Siberia. In the 1990s some radiocarbon data testified that the mammoths on the Wrangel Island existed for a long time during the Holocene from 8000 till 3700 y. BR The present radiocarbon data show that wild horses inhabited the north of Eastern Siberia (the lower stream of the Enissey river, the Novosibirskie Islands, the East Siberian sea-shore) 3000-2000 y. BR Musk-oxen lived on the Taimyr Peninsula and the Lena River delta about 3000 y. BR Some bison remains from Eastern Siberia belong to the Holocene. The following circumstances could promote the process of preservation of the Mammoth fauna representatives. The cool and dry climate of this region promotes the maintenance of steppe associations - habitats of those mammals. The Late Paleolithic and Mesolithic settlements are not found in the Arctic zone of Eastern Siberia from the Taimyr Peninsula to a lower stream of the Yana River; they are very rare in the basins of the Indigirka and Kolyma Rivers. So, the small number of the Stone Age hunting tribes on the North of Eastern Siberia was another factor in the long-term preservation of some Mammoth fauna representatives. Capaccioniazzati, R., S. Villoramoreno, et al. (1991). "Distributional Patterns of Polychaeta in the Alfaques Inlet (Ebro River Delta - Western Mediterranean) - Faunistic and Coenotic Analysis of an Estuarine System." Bulletin of Marine Science 48(2): 369-375. Polychaetous annelids associated with soft bottoms in the Alfaques inlet (Ebro river Delta, western Mediterranean) were studied to evaluate species composition and spatial distribution by cluster classification and Principal Component Analysis (PCA). Spatial distribution by PCA explains more than 63% of the variance through seven axes. Cluster classification using physicochemical parameters distinguished two main assemblages, one extending through central inlet's corridor, deeper than 2 m with less than 60% sand, and a second shallower with sand content greater than 60%. Cluster classification identified four distinct groups. The first group comprised sampling stations in the outer sector with only infaunal species ubiquitous in soft bottoms. The second group can be considered as a subgroup of the previous assemblage with infaunal species typical of polluted sediments. A third set presented a diverse fauna and with could not be characterized from the coenotic standpoint. The fourth group possessed more than 20 species, none of which was found in stations belonging to the former groups. Conway, K. W., J. V. Barrie, et al. (2004). "Modern siliceous sponge reefs in a turbid, siliciclastic setting: Fraser River delta, British Columbia, Canada." Neues Jahrbuch Fur Geologie Und Palaontologie-Monatshefte(6): 335-350. Siliceous sponges have formed reefs within the prodelta of the Fraser River, British Columbia, Canada, in an area where sedimentation rates adjacent to the reef site are greater than 2 cm per year. These newly discovered reefs differ in important ways from those described previously from the northern British Columbia continental shelf. The reefs consist of roughly circular inter-connected mounds up to 14 m in height and 200 m in diameter, found in water depths of 150-190 m and restricted to the top and flanks of an isolated promontory in the midst of the rapidly expanding Holocene prodelta. Two species of hexactinosidan sponge, Aphrocallistes vastus and Heterochone calyx, build a framework of densely packed sponge skeletons while several other species of hexactinellida and demosponges are accessory fauna. Morphologic differences in the framebuilding species are seen as responses to the extremely different environmental conditions of the sediment starved northern shelf and the turbid delta habitats. deGamero, M. L. D. (1996). "The changing course of the Orinoco River during the Neogene: A review." Palaeogeography Palaeoclimatology Palaeoecology 123(1-4): 385-402. Recent studies have revealed that the rich fresh-water vertebrate fossil fauna of the Urumaco Formation in northwestern Falcon, of Late Miocene age, belongs biogeographically to the Orinoco River system. This finding, together with other evidence, can be used to chart the changing course of the Orinoco River during the Neogene and thus date the uplift of various mountain ranges that affected the change in this course. Presence of the Misoa delta in the Middle Eocene of the Maracaibo Basin has been suggested as evidence for a large river, running in a south-north direction and draining the Central Cordillera of Colombia and the Guayana Highlands. The late Middle Eocene uplifting of Western Venezuela changed the paleogeographic setting, and a new delta-building shifted to the south, represented by the extensive Carbonera Formation of Late Eocene to Oligocene age in the Llanos Basin of Colombia and Southwestern Venezuela. In the earliest Miocene, the Falcon Basin, situated to the east of the Maracaibo Basin, was primarily the site of marine shale sedimentation. Stratigraphic and microfaunal evidence suggests the possibility of the presence of the proto-Orinoco River in the western margin of the basin. In any case, from the mid Early Miocene until the end of the Middle Miocene, a fluvio-deltaic sequence was deposited in the northwestern Falcon, with a total thickness of 4.7 km. The Urumaco Formation overlies this sequence and its vertebrate fauna indicates that the river which built the prior delta was definitely the proto-Orinoco. The deformation and uplift of the Eastern Cordillera of Colombia and of the southwestern end of the Merida Andes caused the distal course of the river to be deflected to a west-east direction. A late Middle Miocene age for this change of course is precisely dated on marine microfaunal evidence. The Late Miocene sedimentary record of the Orinoco River delta appears east of Maturin, in the Eastern Venezuela Basin, and Pliocene and Pleistocene deltaic sediments are especially evident in Trinidad and the Columbus Basin. Delgado, M. and M. Alcaraz (1999). "Interactions between red tide microalgae and herbivorous zooplankton: the noxious effects of Gyrodinium corsicum (Dinophyceae) on Acartia grani (Copepoda : Calanoida)." Journal of Plankton Research 21(12): 2361-2371. Gyrodinium corsicum is a dinoflagellate responsible for recurrent water discolourations during winter in Alfacs Bay (Ebre River delta, NW Mediterranean). Since first detected in 1994, episodic mortality of mussels and fish was attributed to this organism, although no direct evidence was obtained. In order to establish the direct role of the dinoflagellate in the mortality of marine fauna, we have studied the effects of G.corsicum on a potential predator, the co-occurring planktonic copepod Acartia grani. Female A.grani were exposed to different concentrations of intact cells, and <5 mu m and <0.2 mu m filtrates of the dinoflagellate. At concentrations of greater than or equal to 3100 cells ml(-1), G.corsicum reduced feeding and egg production rates, and caused paralysis and death of A,grani. Low dinoflagellate concentrations (630 cells ml(-1)) or the <5 mu m and <0.2 mu m filtrates were harmless, at least for the duration of the experiment. Our study demonstrated that a possible poisoning effect due to the ingestion of the dinoflagellate by the copepod must be disregarded, and the toxic effects of soluble substances excreted by the dinoflagellate, or accompanying free-living toxic bacteria, were not causes of copepad paralysis and death. Scanning electron microscopy of female A.grani exposed to G.corsicum indicated a clear tendency of the dinoflagellate to adhere to the copepod cuticle at preferential zones like the urosome and the antennae. Apparently, direct contact between the copepod and the dinoflagellate is a prerequisite for the noxious effects. Amongst other ecological consequences, the development of G.corsicum blooms represents a drastic reduction of grazing pressure in the system through the control of the herbivorous populations. Whether mechanical or chemical effects are the primary reasons for the observed effects is unknown, and to elucidate this will require further research. Fefelov, I. V. (1999). "Transformation of landscapes in the Selenga
River delta and changes in the fauna of birds of prey." Russian Journal
of Ecology 30(5): 351-353. Three biofacies were recognized in samples collected at a depth of 10cm along three transects from the marshes of the Fraser River delta, British Columbia. These biofacies, defined by comparison with those previously identified from surface marsh samples, correspond to three elevational zones: the High Marsh Zone, characterized by the Jadammina macrescens biofacies; the Lower High Marsh Zone, characterized by the Ammonia beccarii biofacies; and the Low Marsh Zone, characterized by the Miliammina fusca biofacies. A dramatic decrease in the abundance of Ammonia beccarii at 10cm depth suggests that the calcareous tests of this species are poorly preserved in the low pH subsurface sediments. As a result, the Ammonia beccarii biofacies will no longer be recognizable after extended burial. Although fewer biofacies can be resolved from paleomarshes of the Fraser delta than at the surface, it is still possible to differentiate between a High Marsh fauna (>+0.94m above mean sea level) and a Low Marsh fauna (<+0.94m above mean sea level). Kamaltynov, R. M. (1999). "On the higher classification of Lake Baikal amphipods." Crustaceana 72: 933-944. A new system of higher taxa of Baikalian amphipods is proposed. This fauna forms a monophyletic part of the superfamily Gammaroidea Leach, 1814 (sensu Bousfield, 1977) and now comprises: Acanthogammaridae Garjajeff, 1901 (with the subfamilies: Acanthogammarinae Garjajeff, 1901, Abyssogammarinae n. subfam., Eulimnogammarinae n. subfam., Hyalellopsinae n. subfam., Odontogammarinae n. subfam., Plesiogammarinae n. subfam., Parapallaseinae n. subfam., and Poekilogammarinae n. subfam.), Macrohectopidae Sowinsky, 1915, Micruropidae n. fam., and Pachyschesidae n. fam. The amphipod fauna of Lake Baikal consists of 50 genera, 261 species, and 73 subspecies. One genus, 4 species, and 8 subspecies of Baikalian origin are endemic to the Angara River and one species is endemic to the Yenisey River delta. The total number of taxa of Baikalian amphipods is now 4 families, 8 subfamilies, 51 genera, 265 species, and 81 subspecies. Liebig, P. M., T. S. A. Taylor, et al. (2003). "Bones on the beach: Marine mammal taphonomy of the Colorado Delta, Mexico." Palaios 18(2): 168-175. How well does a death assemblage of marine mammal bones reflect the diversity, species composition, and proportion of bone types in the living fauna? Marine mammal remains were surveyed along the beaches of the Colorado River delta, Baja California, Mexico. Three carcasses and 470 bones were found among 112 localities along 4.0 kin of shoreline. The location of each site was recorded and each bone was identified, photographed, and measured and its taphonomic condition was noted. The proportion of bone types found was compared to the proportions known in living marine mammals. The list of species found as bones was compared to the list of species known to live in the northern Gulf of California. The maximum skeletal ratio of skull:vertebrae:ribs.phalanges:girdles/limbs in a typical Gulf of California marine mammal is 1:74:30:56:16. The 28 skulls and 442 post-cranial bones found provided a skeletal ratio of 1:12:3:1:1. Although vertebrae are the most common bones in the bone assemblage, only 316 were found, not the similar to2,000 predicted by the 28 skulls, indicating that vertebrae are under-represented. Therefore, skulls provide the best estimate of the minimum number of individuals. Smaller bones appear to be more easily destroyed, buried, or transported away. Most vertebrae were in good condition, suggesting that most bones arrived on the beach recently. Remains of 8 of the 18 species recorded in the northern Gulf were found: Zalophus californianus (California Sea Lion, 8 skulls), Delphinus delphis (Common Dolphin, 7 skulls), Tursiops truncatus (Bottlenose Dolphin, 6 skulls), Phocoena sinus (Vaquita, four skulls), Pseudorca crassidens (False Killer Whale, one skull), Kogia breviceps (Pygmy Sperm Whale, one skull), and a possible Mesoplodon sp. (Beaked Whale, one skull). One Physeter macrocephalus (Sperm Whale) was identified by its large vertebrae. Differences in population size, habitat use, and behavior among species may affect species composition and abundance within the bone assemblage. Migrants and rare species are not as abundant as residents in the bone assemblage. Coastal species are more common than oceanic ones. Marine mammal remains are common within the 3% of Colorado Delta shoreline surveyed, and provide a remarkably good sample of the living fauna. Surveys of mammal remains may be a valuable and cost-effective supplement to aerial and nautical surveys of the live fauna. Lovvorn, J. R. and J. R. Baldwin (1996). "Intertidal and farmland habitats of ducks in the Puget Sound region: A landscape perspective." Biological Conservation 77(1): 97-114. In managing coastal ecosystems, adjacent uplands have been considered mainly as sources of materials affecting littoral environments, and not as parts of an integrated system of habitats directly used by semiaquatic fauna. Agriculture is often viewed as detrimental to coastal habitats, but many waterbirds use both marine and farmland habitats on a daily and seasonal basis. We investigated the importance to dabbling ducks (Anatini) of the juxtaposition of farmland and intertidal habitats in the Puget Sound region of USA and Canada. When feeding in intertidal areas of the Fraser River Delta in British Columbia, wintering dabbling ducks ate mainly the exotic eelgrass Zostera japonica and appeared to avoid the native Zostera marina. Biomass of Z. japonica leaves was insufficient to support herbivorous American wigeon Anas americana throughout winter. Intertidal invertebrates might be adequate to support omnivorous northern pintail A. acutus, mallard A. platyrhynchos and green-winged teal A. crecca, but invertebrate biomass declined substantially in winter. A switch by these ducks from feeding in intertidal areas in autumn to farmland in winter might have resulted from inadequate or much reduced food resources in intertidal areas. Throughout the Puget Sound region, intertidal habitats with adjacent farmland supported about 75% of wigeon, 94% of pintail, 93% of mallard and 92% of teal, and few sites that lacked farmland supported substantial numbers of these species throughout winter. Radio-tagged wigeon and pintail moved among coastal sites even in a mild winter, and temperature patterns over 60 years suggest that ice cover on marine bays and flooded farmland forces dabbling ducks to leave the Fraser Delta in about 13% of all winters to seek alternative sites. For dabbling ducks in this region, it appears that farmland adjacent to intertidal areas is an important component of coastal habitat complexes, and a system of alternative sites should be included in regional landscape plans. Copyright (C) 1996 Published by Elsevier Science Ltd Marchini, A., K. Gauzer, et al. (2004). "Spatial and temporal variability of hard-bottom macrofauna in a disturbed coastal lagoon (Sacca di Goro, Po River Delta, Northwestern Adriatic Sea)." Marine Pollution Bulletin 48(11-12): 1084-1095. The sessile and mobile macrobenthos on artificial hard bottoms was studied in 12 stations of the Sacca di Goro lagoon, a brackish, highly stressed water basin in the delta of the river Po, open to the Northwestern Adriatic Sea. Three sampling surveys were carried out in June and September 2000 and June 2001 in order to make three types of temporal comparisons: (i) on a seasonal scale, before and after a summer dystrophic event; (ii) on an annual basis, before and after the works of excavation of a canal through the outer sand bank; (iii) on a multiannual scale, comparing the data with those of a survey carried out in 1988. The biocoenoses did not show large fluctuations after a moderately severe summer dystrophic crisis, while the digging of the canal caused clear changes in the macrobenthos community structure after one year. The long-term comparison showed a shift in the community patterns after a decade. (C) 2003 Elsevier Ltd. All rights reserved. Muoria, P. K., G. M. Karere, et al. (2003). "Primate census and habitat evaluation in the Tana delta region, Kenya." African Journal of Ecology 41(2): 157-163. Nineteen indigenous forest patches in the Tana River delta region, Kenya were surveyed between October and November 2000 for primates and habitat disturbance. Special emphasis was placed on the endangered Tana River red colobus (Procolobus rufomitratus Peters) and crested mangabeys (Cercocebus galeritus galeritus Peters), both of which are endemic to the region. Habitat disturbances evident in the forests included cutting of trees, harvesting of thatching material, firewood collection, dyke construction, cultivation, palm wine tapping and charcoal burning. A total of 85 groups of five primate species were counted. These comprised eighteen, ten, 22, 31 and four groups of red colobus, crested mangabey, baboons (Papio cynocephalus L.), sykes monkeys (Cercopithecus mitis Wolf) and vervet monkeys (Cercopithecus aethiops L.), respectively. A wider distribution of red colobus and crested mangabeys than was documented previously was noted, implying that they are probably more abundant than hitherto reported. It is hypothesized that extensive studies on some fauna considered endangered world-wide would probably redefine their conservation status. Future studies in the lower Tana River region should cover the previously unsurveyed forests and focus on ways of curbing forest destruction. Ni, I. H. and K. Y. Kwok (1999). "Marine fish fauna in Hong Kong waters." Zoological Studies 38(2): 130-152. Marine fish fauna in Hong Kong Waters. Zoological Studies 38(2). 130-152. Rapid industrialization and large-scale infrastructural projects in Hong Kong and the Pearl River Delta in recent years have placed an extraordinarily heavy burden on coastal environments. The magnitude of the problem will increase as sewage discharge, ocean dredging/disposal, and land reclamation continue to expand in the next few years. Fundamentals of marine environmental impact assessment are based upon a good understanding of biodiversity that allow us to monitor environmental changes. However, there is no baseline data on marine fauna that allow evaluation of the damage from various large-scale infrastructural projects to aquatic environments. A comprehensive database on local fish fauna is, therefore, urgently necessary for the planning and implementation of conservation strategies in Hong Kong. This paper is the ist systematic report on marine fish fauna in Hong Kong waters. From years of opportunistic fishing surveys and a thorough literature review, a total of 25 orders, 124 families, 390 genera, and 834 fish species in Hong Kong waters were identified. There are 97 fish species listed herein as new records to the area. Otvos, E. G. and M. J. Giardino (2004). "Interlinked barrier chain and delta lobe development, northern Gulf of Mexico." Sedimentary Geology 169(1-2): 47-73. A wealth of new data provides a well-constrained chronology of mid- to late Holocene coastal development in the Louisiana-Mississippi borderland that may also be utilized in a globally applicable sedimentation model. Barrier sand and deltaic mud sequences illustrate a process by which potential ground water and hydrocarbon reservoir rocks accumulated unusually rapidly and were preserved. Set against decelerating Holocene sea-level rise and locally variable subsidence rates, the study provides an example of the interplay between an emerging, prograding, and partially stranded barrier island chain, a sizable estuary, and several extensive delta lobes. Utilizing microfossil fauna-based depositional facies information and archaeological data, absolute dates helped to reconstruct the history of the Alabama-Louisiana barrier chain and deltas between ca. 5.7 and ca. 1.5 C-14 ka BP. Protected by the substantial dune cover that prevented island submersion, the regional eustastic transgression paradoxically was synchronous with significant progradational barrier and deltaic regression. The earliest barrier islands emerged ca. 4.6-4.4 C-14 ka BP (ca. 5.7-5.0 cal years) when sea level stood at ca. - 1.0 to - 1.5 m. These islands isolated Mississippi Sound from the greater Gulf of Mexico. The absence of a lagoonal-inshore sediment interval beneath the islands and the 3-15 m thick basal nearshore marine muddy-sandy unit that blankets the Pleistocene surface refutes the transgressive history of barrier initiation. The islands aggraded on a 3.0-16.5 m thick fine sandy shallow-marine regressive platform lithosome that, in turn, overlies a transgressive muddy-sandy nearshore marine lower sediment interval. Avulsion of the Mississippi River had abruptly reduced nearshore salinities by ca. 3.9-3.7 ka C-14 BP. Renewed Mississippi delta growth induced rapid aggradation and progradation on the opposite Pearl River delta-mainland shore as well. Gulf influences have rapidly diminished in areas so affected. A new absolute chronology of the Mississippi-St. Bernard delta lobes constrains these events. Delta growth and mainland progradation first isolated, then severely constricted the Lake Borgne embayment. Accompanied by ongoing subsidence, the western barriers were stranded, then buried. Shoaling, related to St. Bernard delta progradation, interfered with westward littoral drift to maintain Cat Island. Archaeology provided important supplementary data for dating environmental changes. Refuting earlier suggestions that Native colonization rapidly followed delta complex formation, the earliest known Indian sites postdated the start of the associated St. Bernard delta lobe by 1.9-3.1 C-14 ka. (C) 2004 Published by Elsevier B.V. Reinhardt, E. G., D. J. Stanley, et al. (1998). "Strontium isotopic-paleontological method as a high-resolution paleosalinity tool for lagoonal environments." Geology 26(11): 1003-1006. A combined strontium isotopic (Sr-87/Sr-86) and paleontological method is newly applied to a modern lagoon in Egypt's Nile River delta to test its applicability as a paleosalinity proxy. Analyses of 22 surficial samples collected throughout the lagoon include 81 Sr isotopic analyses of mollusks, foraminifera, ostracods, barnacles, bryozoans, serpulid worm tubes, pore water, and gypsum crystals. Two salinity groups are distinguished in each sample: a lower salinity group (similar to 1 ppt) mixed with a higher salinity group (similar to 3-10 ppt) that, respectively, are interpreted as the modern biocoenosis and an older relict fauna. The relict fauna denotes higher salinity conditions in the lagoon prior to closure of the Aswan High Dam (1964), and the modern fauna records freshening of the lagoon. Recent decreased salinity is a response to regulated Nile River flow and increased discharge into Manzala of fresh water via canals and drains. Quantification of this short-term salinity change holds promise for study of modern lagoons in other world settings, and may provide paleoclimatic information for older lagoon sequences in the Nile River delta and the geologic record. Risnoveanu, G. and A. Vadineanu (2003). "Long term functional changes within the Oligochaeta communities within the Danube river delta, Romania." Hydrobiologia 506(1-3): 399-405. Within the Danube River delta's lakes the Oligochaeta communities comprise between 7.9% and 36.2% of the total biomass of benthic fauna. Their importance in energy flow at the ecosystem level changed in relation to fast trophic transition of all shallow lakes to the hypertrophic state. The parameters of the energy budget of the dominant populations and the potential production of benthivorous fish species assessed during 1976-1994 interval support this conclusion. P/B ratio, K-1 and K-2 coefficients assessed for both the 1976-1980 and 1991-1994 intervals revealed different functional patterns of response of Potamothrix hammoniensis (Michaelsen, 1901) and Limnodrilus hoffmeisteri (Claparede, 1862) to varying trophic conditions. Changes in communities structure, size of the constituent populations and their age distribution, as well as the quantity and quality of food supply and level of hypoxia at the sediment/water interface were the main factors that affected the role of these populations as energy carrier from the huge energy pool represented by sedimented organic carbon to benthivorous fish species. Tafe, D. J. (1990). "Zooplankton and Salinity in the Rufiji River Delta, Tanzania." Hydrobiologia 208(1-2): 123-130. A comparative analysis of the zooplankton from different salinities was carried out in the Rufiji River delta system, located on the mid Tanzanian coastline opposite Mafia Island (7-degrees 45' S, 39-degrees 20' W). Zooplankton samples were collected by vertical, oblique and horizontal surface tows (250-mu-m mesh) at three sites, namely at the river mouth (salinity = 20-25%), in the estuary (salinity = 12-14%), and in the upper reaches of the river (salinity = 0%). Samples taken in the river mouth and estuary were collected at two times of the day, which coincided approximately with midday and sunset. A comparison of zooplankton diversity and abundance at the three sites showed that a much richer, more diverse fauna existed at the river mouth and estuary compared to the upper reaches. The zooplankton collected both at the mouth and in the estuary were very abundant at certain times of the day, although differences in faunal composition were found between the two sites. Wells, T. M., A. S. Cohen, et al. (1999). "Ostracode stratigraphy and paleoecology from surficial sediments of Lake Tanganyika, Africa." Journal of Paleolimnology 22(3): 259-276. We report here on the first detailed ostracode stratigraphic record to be obtained from late Holocene sediments of Lake Tanganyika. We analyzed four cores, three from the northern lake region and a fourth from a more southern lake locality, that collectively record ostracode assemblages under a variety of disturbance regimes. These cores provide a stratigraphic record of ostracode abundance and diversity, as well as depositional changes over time periods of decades to millennia. We have investigated the fossil ostracodes in these cores by looking at temporal changes of species diversity and population structure for the species present. All four cores provided distinct patterns of ostracode diversity and abundance. BUR-1, a northern lake core obtained close to the Ruisizi River delta, yielded a sparse ostracode record. Karonge #3, another northern core from a site that is closely adjacent to a river delta with high sediment loading, yielded almost no ostracodes. The third core 86-DG-14, taken from a somewhat less disturbed area of the lake, suggests that there have been recent changes in ostracode populations. Through most of the lower portion of this core, ostracode abundance is low and species richness is relatively constant. Above 7 cm there is a marked increase in ostracode abundance and a corresponding decrease in species richness, probably signaling the onset of a major community disturbance, perhaps due to human activities. The southernmost core, 86-DG-32, is from a site that is well removed from influent rivers. Ostracode abundance varies erratically throughout the core, whereas species richness is relatively constant and high throughout the core. The temporal variation evident in ostracode community makeup both within and between the studied cores may be a result of naturally patchy distributions among ostracodes, coupled with local extinctions and recolonizations, or it may reflect inadequate sampling of these high diversity assemblages. In either case, these cores illustrate the potential to obtain high resolution ostracode records from the rich, endemic fauna of Lake Tanganyika that can be used to address questions about the history of community structure and human impacts in this lake. |
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