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L'étude présente les cartographies de l'occupation du sol de la réserve de biosphère du Ferlo (créée en 2012) réalisées, par interprétation visuelle, à partir d'images satellitaires (Arcgis et Corona) prises en 1965 et 2017. Douze modes (ou classes) d'occupation du sol ont été distingués : ripicole relique, savane boisée, savane arborée, savane arbustive à arborée, savane arbustive, steppe arbustive à arborée, steppe arborée, steppe arbustive, sol et roche à nu, culture pluviale et jachère, habitat, mare. Les formations végétales spontanées couvraient 96 % de la superficie totale en 1965 et encore plus de 94 % en 2017. Toutefois cette stabilité relevée pour l'ensemble de la végétation spontanée s'est accompagnée d'une forte évolution des différents types de couvert. Sur les presque 1 914 000 ha occupés par la végétation spontanée en 1965, 38,2 % sont restés rattachés à la même classe d'occupation du sol entre les deux dates, 42,1 % ont subi une évolution négative (surtout au nord et à l'extrême sud) et 19,7 % une évolution positive (surtout au sud-ouest). Les savanes arbustives à arborées restent dominantes (environ 687 000 ha en 1965 et 603 000 ha en 2017), mais les steppes arbustives ont beaucoup progressé (environ 240 000 ha en 1965 et 497 000 ha en 2017). Nous retrouvons ici la dégradation du couvert végétal commune à l'ensemble du Sahel. Plus qu'aux conditions naturelles (la sécheresse qui est apparue au début des années 1970), cette évolution semble due à la présence maintenant continue au Ferlo de populations jadis transhumantes. The study presents land cover maps of the Ferlo Biosphere Reserve (created in 2012) made by visual interpretation from satellite images (Arcgis and Corona) taken in 1965 and 2017. Twelve land cover patterns (or classes) were identified: riparian relic forest, woody savannah, tree savannah, shrub savannah with trees, shrub savannah, tree steppe, shrub steppe with trees, shrub steppe, bare soil and rock, rainfall crop and fallow, habitat, pond. The spontaneous vegetation formations covered 96 % of the total area in 1965 and still more than 94 % in 2017. However this stability of the land cover by the spontaneous vegetation, was accompanied by a strong evolution of the different types of cover. Of the nearly 1,914,000 ha inhabited by spontaneous vegetation in 1965, 38.2 % retained the same land cover class between the two dates, 42.1 % have decreased (especially in the north and extreme south) and 19.7% have increased (especially in the south-west). Shrub savannahs with trees remain dominant (about 687 000 ha in 1965, about 603 000 ha in 2017), but the shrub steppes have increased significantly (about 240 000 ha in 1965, about 497 000 ha in 2017). We find here the degradation of vegetation cover common to all the Sahel. More than natural conditions (the drought that appeared in the early 1970s), this evolution seems to be due in Ferlo to the presence, now continuously, of formerly transhumant populations.

L'article analyse l'évolution spatio-temporelle des inondations dans la zone urbaine de Douala (Cameroun) à partir d'une approche géohistorique. Une base de données sur les inondations est créée à l'aide d'informations issues de la presse (du journal Cameroon Tribune) ; elle permet de spatialiser les événements pour comprendre quels sont les quartiers de Douala les plus fréquemment inondés. On observe ainsi une augmentation du nombre d'inondations rapportées depuis les années 2010, qui semble corrélée à l'évolution de l'emprise urbaine de la ville. Les zones urbaines inondées de façon récurrente sont le plus souvent les quartiers informels construits directement en zones inondables et dont l'accroissement est important depuis les années 1990. Les données de la presse ont aussi permis d'étudier l'évolution du discours sur les politiques de gestion du risque d'inondation. Celles-ci restent fortement focalisées sur la résolution des crises, malgré le contexte des politiques d'adaptation au changement climatique qui développent des projets d'amélioration de la gestion urbaine des inondations. The article analyzes the spatio-temporal evolution of floods in the urban area of Douala (Cameroon) from a geohistorical approach. A database on floods is created using information from the press (from Cameroon Tribune journal), it allows to spatialize the events to understand which areas of Douala are the most frequently flooded. There has been an increase in the number of floods reported since 2010, which seems to correlate with the evolution of the city's urban footprint. Recurrently flooded urban areas are most often the informal neighborhoods built directly into flood-prone areas and whose growth has been significant since the 1990s. Data from the press also helped to study the evolution of the discourse on flood risk management. It remains strongly focused on crisis resolution, despite the context of climate change adaptation policies that develop projects to improve urban flood management.

La culture de la vigne a été développée en Algérie par la colonisation française. À l'indépendance, en 1962, le vignoble algérien, à destination vinicole, couvrait plus de 350 000 ha dont l'essentiel de la production était écoulé en France. Sur le territoire de la future wilaya de Mostaganem (2269 km2), 49030 ha étaient alors couverts de vignes, en particulier sur le plateau de Mostaganem.La perte du marché français à la fin des années 1960 a provoqué une réduction très forte du vignoble. Ce déclin n'a fait que s'aggraver jusqu'aux mesures adoptées en 2000 pour soutenir l'agriculture.Afin d'analyser l'évolution des superficies plantées en vigne, une étude diachronique a été menée à partir de cartes topographique (1958 et 1983) et d'images satellitaires Google Earth Pro (2017).Les résultats mettent en évidence un effondrement des superficies entre 1958 et 1983. Le vignoble s'est encore rétracté entre 1983 et 2017, date à laquelle il ne couvre que 6190 ha. Mais l'examen des parcelles présentes en 1983 qui ont disparu en 2017, confirme que le déclin du vignoble a été maximal à la fin des années 2000.L'évolution du vignoble s'est également traduite par une profonde mutation spatiale. Les communes du plateau de Mostaganem et plus encore des plaines des Bordjias ont subi des pertes relatives considérables. Au contraire, les vignes ont mieux résisté dans les communes littorales du nord et les superficies ont même augmenté entre 1983 et 2017 dans certains secteurs des monts du Dahra.Malgré le regain récent, l'avenir du vignoble reste incertain dans un pays où la religion interdit la consommation de vin et juge sévèrement sa production. The cultivation of vines was developed in Algeria by French colonization. At independence in 1962, the Algerian vineyard, for wine production, covered more than 350.000 ha, most of whose production was sold in France.On the territory of the future wilaya of Mostaganem (2.269 km2), 49.030 ha were then covered with vines, particularly on the Mostaganem plateau.The loss of the French market at the end of the 1960s has caused a very significant reduction in the vineyard. This decline has only worsened until the measures adopted in 2000 to support agriculture. In order to analyse the evolution of the areas planted with vines, a diachronic study was carried out using topographic maps (1958 and 1983) and Google Earth Pro satellite images (2017).The results show a collapse of the areas between 1958 and 1983. The vineyard retracted again between 1983 and 2017, when it covered only 6.190 ha. But an examination of the parcels present in 1983, which disappeared in 2017, confirms that the decline in the vineyard was greatest at the end of the 2000s.The evolution of the vineyard has also resulted in a profound spatial mutation. The communes of the Mostaganem plateau and even more so of the Bordjias plains have suffered considerable relative losses. On the contrary, vines have been more resilient in the northern coastal municipalities and areas have even increased between 1983 and 2017 in some areas of the Dahra Mountains.Despite the recent revival, the future of the vineyard remains uncertain in a country where religion prohibits the consumption of wine and severely judges its production.

International audience; This paper proposes an approach of climate change impacts assessment on overflow of an Ourthe river reach (Belgium). We based our work on a set of hydro-climatic scenarios including the long-term climate variability (from the Maunder Minimum to the end of the 21st century). A 1D hydraulic modelling (the WOLF 1D model) is then useful to detect an overflowing discharge along the reach, and a discharge-duration-frequency analysis was implemented to consider the flood dynamic (duration of overflow) in the impact study. From comparison between baseline data (1976-2005) corresponding to present climate to hydro-climate scenarios, impacts on overflow characteristics (duration and frequency) are analyzed. Results show that in a context of changing climate conditions, frequency of short overflow events decrease whereas that of long overflow events increase. The results of this study are useful to flood risk managers who aim to add "climatic resilience" to river planning measures.; Cet article propose une quantification/qualification des impacts d'un climat en évolution sur les débordements d'un tronçon de l'Ourthe (Belgique), à partir d'un jeu de scénarios hydro-climatiques intégrant la variabilité long terme du climat (du Minimum de Maunder jusqu'à la fin du XXIème siècle). À l'aide de la modélisation hydraulique 1D (modèle WOLF 1D), un débit débordant est identifié le long du tronçon. Puis l'analyse débit-durée-fréquence est utilisée pour intégrer la dynamique de crue (durée de débordement) dans l'étude d'impact. En comparant un scénario de référence correspondant au climat actuel (1976-2005) à notre jeu de scénarios hydro-climatiques, les changements en durée et fréquence dans les débordements sont analysés. Il ressort de cette analyse que dans un contexte de variabilité climatique long terme, les débordements courts sont en majorité moins fréquents, tandis que les débordements longs sont en majorité plus fréquents. Les résultats de cette étude sont utiles aux gestionnaires du risque d'inondation qui souhaitent apporter de la "résilience climatique" aux aménagements des cours d'eau destinés à gérer les débordements.

Les sédiments du plateau des Guyanes témoignent de phénomènes climatiques extrêmes : 1/ climats interglaciaires équatoriaux chauds et humides du Pléistocène (depuis 50000 ans BP) et du Postglaciaire qui entraînent une période de biostasie sur le continent et 2/ climats plus secs entre 30000 et 20000 ans BP au cours desquels se développe une période de rhexistasie, écho du Dernier Maximum Glaciaire (DMG).Ces bouleversements climatiques majeurs affectent notre planète et en particulier les Guyanes et le débouché de l'Amazone, marqués par le niveau variable des océans : submersion et exondation rythment l'histoire régionale. Lors du DMG, l'Amazone emprunte le canyon sous marin orienté nord qui prolonge sur la plate-forme le cours du fleuve. Les eaux, déviées vers le nord-ouest par les courants côtiers, longent la plate-forme des Guyanes désormais exondée, couverte de vallées fluviales, milieux deltaïques, lagunes, mangroves. Une barrière récifale, discontinue au droit des estuaires, borde le littoral dans des eaux chaudes et claires. Lors de la transgression de la fin du Pléistocène et durant l'Holocène inférieur, les eaux turbides de l'Amazone envahissent progressivement la plate-forme provoquant l'agonie des récifs. La transgression s'achève à l'Holocène supérieur.Les dépôts amazoniens couvrent désormais la partie interne du plateau des Guyanes affichant leur originalité, personnalisés par la présence de verdines (argiles phylliteuses), typique authigenèse régionale, et par la spécificité des cortèges argileux en milieu océanique, écho lointain de El Niño, qui demeure un signal climatique majeur affectant l'Amérique du Sud septentrionale et le golfe du Mexique. The sediments of the Guianas shelf testify to extreme climatic events: 1/ warm and humid equatorial interglacial climates during the Pleistocene (since 50000 BP) and the postglacial that cause to a biostasy period on the continent and 2/ drier climates between 30000 and 20000 BP during which develops a rhexistasy period, echo of the Last Glacial Optimum (LGM).These major climatic changes affect our planet and in particular the Guianas and the Amazon mouth. These latest are marked by a variation of the level of the oceans with submersion and exundation which rhythm the regional history. During the LGM, the Amazon borrows the north-facing submarine canyon that extends on the platform the course of the river. The waters diverted to the northwest by the coastal currents along the Guianas platform now emerged, covered with river valleys, deltaic environments, lagoons, and mangroves. A reef barrier discontinuous in front of estuarine areas, borders the shoreline in warm and clear waters. During the transgression of the end of the Pleistocene and the early Holocene, the turbid waters of the Amazon gradually invade the platform causing the agony of the reefs. The transgression ends during the late Holocene.Amazon deposits now cover the inner part of the Guianas shelf and display their originality. The latter is reflected by the presence of verdine, typical regional authigenesis, and by the specificity of clay associations in oceanic environment. This assemblage represents a distant echo of El Niño-Southern Oscillation, which remains a major climatic signal affecting Septentrional South America and the Gulf of Mexico.

Selon de nombreuses prévisions, les rivières méditerranéennes devraient être soumises dans les années à venir à de fortes pressions environnementales liées aux changements climatiques, ce qui laisse entrevoir des conséquences certaines pour la faune qu'elles hébergent. Pour tenter de percevoir ces conséquences, la faune invertébrée de l'une de ces rivières, la Cèze, a été étudiée en période d'étiage. La biodiversité des assemblages de la Cèze a été estimée en tenant compte de l'hétérogénéité des échanges entre la rivière et sa nappe. Ainsi trois habitats ont été échantillonnés : le fond de la rivière (habitat benthique), la zone d'interface entre la rivière et l'aquifère poreux (zone hyporhéique) et celle d'interface avec l'aquifère karstique (sources). Les résultats montrent que la composition des assemblages d'espèces récoltées est différente dans les trois habitats, avec seulement 11 % de taxons communs. L'habitat benthique se révèle plus riche en Éphéméroptères et en Trichoptères, l'habitat hyporhéique en Oligochètes, Crustacés et Plécoptères, et les sources en Diptères. Les espèces stygobies (spécialisées à la vie en milieu souterrain) sont totalement absentes de l'habitat benthique, alors qu'elles sont bien représentées dans les sources et la zone hyporhéique. Les deux habitats situés à l'interface entre le cours d'eau et les systèmes souterrains produisent un enrichissement considérable de la biodiversité du cours d'eau, qui se traduit par un doublement du nombre de taxons par rapport à l'habitat benthique. Ce travail montre que l'intégration des zones situées à l'interface entre la rivière et les eaux souterraines est cruciale pour l'obtention d'une estimation aussi complète que possible de la biodiversité des hydrosystèmes. In a close future, Mediterranean rivers will support strong disturbances due to climate changes, with inexorable consequences for their fauna. The invertebrate biodiversity of the Cèze River (South of France) was studied in a karstic area. The benthic layer (river bottom), the hyporheic layer (interface with the groundwater inside river sediment) and the lateral springs (interface with the karstic systems) were sampled in early summer. Only 11 % of the taxa were sampled simultaneously in the three habitats. Ephemeroptera and Trichoptera were more species rich in the benthic zone; Oligochaetes, crustaceans and Plecoptera in the hyporheic zone and Diptera in the lateral springs. Stygobite species lack in the benthic layer, they were more diversified in the springs and in the hyporheic zone. When all habitats are considered together, the total taxonomic richness is twice of the benthic one. The habitats located at the interface between river and groundwater thus must be included in the river biodiversity estimations.

The Eurasian beaver (Castor fiber) has a greater impact on local ecosystems than other herbivores, and the affected area exceeds the range of its presence. Its activity may change or create new habitats by modifying the availability of the biotic and abiotic resources available not only to beavers, but also to other groups of animals. Our aim was to study how beaver activity affects the benthos composition in a small river and in a beaver pond. The way in which beavers function in the case of small rivers has received little attention. The study showed a lower density of benthos above the dam (beaver pond - 1467 ind./m2) compared to the river (3147 ind./m2). Below the dam, the diversity of Trichoptera and Coleoptera was greater, while Diptera were more abundant in the beaver pond. Betidae were a constant component in the benthos assemblages and were most abundant in the beaver pond. Collectors-gatherers and predators were the most numerous in the beaver pond. Decreasing percentages of collectors-gatherers were observed with an increased abundance of collectors-filterers and shredders in the river. All of the ratio values except the P/T FFG (Predators to total of all other groups) were lower in the beaver pond compared to the river. The % EPT (Ephemeroptera Plecoptera and Trichoptera) was also greater in the beaver pond. Small differences in the physicochemical properties of the water and organic matter content in the bottom sediments were found both above and below the beaver dam.

Background: There is scarce information about European folk knowledge of wild invertebrate fauna. We have documented such folk knowledge in three regions, in Romania, Slovakia and Croatia. We provide a list of folk taxa, and discuss folk biological classification and nomenclature, salient features, uses, related proverbs and sayings, and conservation. Methods: We collected data among Hungarian-speaking people practising small-scale, traditional agriculture. We studied "all" invertebrate species (species groups) potentially occurring in the vicinity of the settlements. We used photos, held semi-structured interviews, and conducted picture sorting. Results: We documented 208 invertebrate folk taxa. Many species were known which have, to our knowledge, no economic significance. 36 % of the species were known to at least half of the informants. Knowledge reliability was high, although informants were sometimes prone to exaggeration. 93 % of folk taxa had their own individual names, and 90 % of the taxa were embedded in the folk taxonomy. Twenty four species were of direct use to humans (4 medicinal, 5 consumed, 11 as bait, 2 as playthings). Completely new was the discovery that the honey stomachs of black-coloured carpenter bees (Xylocopa violacea, X. valga) were consumed. 30 taxa were associated with a proverb or used for weather forecasting, or predicting harvests. Conscious ideas about conserving invertebrates only occurred with a few taxa, but informants would generally refrain from harming firebugs (Pyrrhocoris apterus), field crickets (Gryllus campestris) and most butterflies. We did not find any mythical creatures among invertebrate folk taxa. Almost every invertebrate species was regarded as basically harmful. Where possible, they were destroyed or at least regarded as worth eradicating. However, we could find no evidence to suggest any invertebrate species had suffered population loss as a result of conscious destruction. Sometimes knowledge pertaining to the taxa could have more general relevance, and be regarded as folk wisdom concerning the functioning of nature as a whole. Conclusions: The high number of known invertebrate folk taxa suggests that it would be worth conducting further investigations in other areas of Europe.

In Poland eleven stygobitic species have been found, whereas in Central Europe their number reached 23 species. Lumbriculidae are represented by 10 species, Enchytraeidae by seven, Naididae by three, whereas Dorydrilidae and Lumbricidae by two and singular species, respectively. Some species are known from Central Europe exclusively, but majority of them have wider distribution.

BackgroundBiogeographical and macroecological principles are derived from patterns of distribution in large organisms, whereas microscopic ones have often been considered uninteresting, because of their supposed wide distribution. Here, after reporting the results of an intensive faunistic survey of marine microscopic animals (meiofauna) in Northern Sardinia, we test for the effect of body size, dispersal ability, and habitat features on the patterns of distribution of several groups.Methodology/principal findingsAs a dataset we use the results of a workshop held at La Maddalena (Sardinia, Italy) in September 2010, aimed at studying selected taxa of soft-bodied meiofauna (Acoela, Annelida, Gastrotricha, Nemertodermatida, Platyhelminthes and Rotifera), in conjunction with data on the same taxa obtained during a previous workshop hosted at Tjärnö (Western Sweden) in September 2007. Using linear mixed effects models and model averaging while accounting for sampling bias and potential pseudoreplication, we found evidence that: (1) meiofaunal groups with more restricted distribution are the ones with low dispersal potential; (2) meiofaunal groups with higher probability of finding new species for science are the ones with low dispersal potential; (3) the proportion of the global species pool of each meiofaunal group present in each area at the regional scale is negatively related to body size, and positively related to their occurrence in the endobenthic habitat.Conclusion/significanceOur macroecological analysis of meiofauna, in the framework of the ubiquity hypothesis for microscopic organisms, indicates that not only body size but mostly dispersal ability and also occurrence in the endobenthic habitat are important correlates of diversity for these understudied animals, with different importance at different spatial scales. Furthermore, since the Western Mediterranean is one of the best-studied areas in the world, the large number of undescribed species (37%) highlights that the census of marine meiofauna is still very far from being complete.

In this research we evaluate the effects of the method used for estimating the potential surface available for benthic macroinvertebrates in macrophyte and unvegetated habitats on several metrics and habitat preference of aquatic macroinvertebrates in the upper catchment of the Henares River (Guadalajara, Central Spain). Three sampling sites were selected: a well-preserved stream (site A), a stream with no wood riparian vegetation (site B), and a straightened and deforested reach (site C). Two habitats were selected in each site: unvegetated habitat (i.e., substrata without macrophytes) and macrophyte habitat (i.e., substrata covered by macrophytes). In each habitat, six macroinvertebrate samples (including all macrophytes or mineral particles) were collected using a Hess sampler. Diversity and density of major families were referred to the surface of the Hess sampler (=Hess surface method) and to the actual surface of either mineral particles or macrophytes (=actual surface method). In general, for the actual surface method, biomass, richness, dominance, and diversity metrics were higher in the mineral habitat than in the macrophyte habitat. This trend was different for the Hess surface method. In general, densities turned out to be higher in the unvegetated habitat than in the macrophyte habitat when using the actual surface method, but the reverse occurred when using the Hess surface method. This fact is relevant for river biomonitoring, especially when reaches with different dominant substrates (macrophytes vs mineral) are compared using just one of the methods. It is concluded that the macrobenthic metrics and density values are influenced by the method used to estimate the potential available surface for aquatic macroinvertebrates.

Invasive plants generally have fewer aboveground pathogens and viruses in their introduced range than in their natural range, and they also have fewer pathogens than do similar plant species native to the introduced range. However, although plant abundance is strongly controlled by root herbivores and soil pathogens, there is very little knowledge on how invasive plants escape from belowground enemies. We therefore investigated if the general pattern for aboveground pathogens also applies to root-feeding nematodes and used the natural foredune grass Ammophila arenariaas a model. In the late 1800s, the European A. arenariawas introduced into southeast Australia (Tasmania), New Zealand, South Africa, and the west coast of the USA to be used for sand stabilization. In most of these regions, it has become a threat to native vegetation, because its excessive capacity to stabilize wind-blown sand has changed the geomorphology of coastal dunes. In stable dunes of most introduced regions, A. arenaria is more abundant and persists longer than in stabilized dunes of the natural range. We collected soil and root samples and used additional literature data to quantify the taxon richness of root-feeding nematodes on A.?arenaria in its natural range and collected samples from the four major regions where it has been introduced. In most introduced regions A. arenaria did not have fewer root-feeding nematode taxa than the average number in its natural range, and native plant species did not have more nematode taxa than the introduced species. However, in the introduced range native plants had more feeding-specialist nematode taxa than A. arenaria and major feeding specialists (the sedentary endoparasitic cyst and root knot nematodes) were not found on A. arenaria in the southern hemisphere. We conclude that invasiveness of A. arenaria correlates with escape from feeding specialist nematodes, so that the pattern of escape from root-feeding nematodes is more alike escape from aboveground insect herbivores than escape from aboveground pathogens and viruses. In the natural range of A. arenaria, the number of specialist-feeding nematode taxa declines towards the margins. Growth experiments are needed to determine the relationship between nematode taxon diversity, abundance, and invasiveness of A. arenaria. [KEYWORDS: Ammophila arenaria ; Ammophila breviligulata ; biotic resistance hypothesis ; enemy escape hypothesis ; feeding specialist ; invasive plant ; root herbivore ; soil pathogen]

Une population protegee d'ecrevisses a pattes blanches, Austropotamobius pallipes pallipes (Lereboullet), a ete etudiee entre 1995 et 1996. 1 511 ecrevisses ont ete collectees au cours de cette etude incluant des captures par nasse et a la main. 356 animaux excedaient la taille legale de capture -90 mm LT (Longueur Totale)-, representant 23,6% des captures. Les Captures Par Unite d'Effort (C.P.U.E.) sont comprises entre 1,2 en fevrier et 8,6 en octobre. Le sex ratio sur les captures est biaise en faveur des femelles (1:1,9). Les mâles sont dominants uniquement durant la periode froide ou la temperature de l'eau est inferieure a 10°C. La thelohaniose semble apparaitre de facon cyclique dans cette population avec de hauts taux d'ecrevisses infestees au cours des etes 1995 et 1996. Aucune ecrevisse infestee n'a ete trouvee entre janvier et mars. Les densites estimees sont comprises entre 4,4 et 2,2 adultes au metre carre. L'accouplement commence au milieu du mois de novembre ou la duree du jour est courte et ou la temperature de l'eau tombe en dessous de 10°C. Les femelles grainees ont une taille comprise entre 58,5 et 100,4 mm de LT. La moyenne du nombre d'oeufs pleopodaux baisse au cours de la periode d'incubation (moyenne = 55 oeufs par femelle en decembre a 30 oeufs en mai). Le maximum d'oeufs est de 85 pour une femelle (85 mm de LT) capturee en novembre. Au cours du debut du mois de mai, 40% des femelles echantillonnees ne portaient pas d'œuf. Tous ces resultats semblent montrer une surdensite d'ecrevisses dans cette population, des recommandations pour la reguler sont discutees.

This study was conducted to examine the benthic invertebrate fauna inhabiting in the subtidal zone in and around the islets of Namuseom and Bukhyeongjeseom off the coast of Busan by SCUBA diving in September 2013. As a consequence, it was confirmed that a total of 6 phyla, 14 classes, 20 orders, 46 families, and 73 species of zoobenthos inhabit in and around those islets. The total number of species surveyed by taxon during the study is 22 species of Arthropoda (30%), 20 species of Mollusca (27%), 15 species of Cnidaria (21%), 10 species of Echinodermata (14%), four species of Poridera (5%), and two species of Chordata.

Biological determinations of water quality have been increasingly used as a measure of water quality rather than chemical determinations. Aquatic invertebrates are very sensitive to changes in their habitat, whether these changes are physical or chemical. The biological method is often capable of detecting minute gradual changes that would escape notice by chemical methods. Chemical analysis of the water quality gives an accurate picture of the chemical pollutants that are present in the water at the particular moment that the sample was taken. However, if this is an isolated chemical analysis of this particular stream, the results may not represent normal conditions of the stream. The invertebrate fauna of a stream not only represents present chemical conditions but also changes in water quality that have occurred in the past. Once a biologist is familiar with a stream, minor changes of water quality are revealed to him by replacement of species by other closely related species or by the gradual disappearance of some species. An overnight chemical discharge may go unnoticed by the chemist but is strikingly apparent to the biologist by the sudden absence of some organisms. By working upstream until these organisms are found, he can pinpoint the position of the chemical overload. This could be monitored chemically only by a great number of tests if the discharge had been noticed in the first place.The studies outlined in this report are G.R.C.A.'s first attempt at detailed biological surveys. The areas chosen for study were picked to determine the effects of reservoirs on the downstream fauna and water quality.