Marshy soil and sediment samples were collected during dry and rainy seasons within Warri, and Agbarho, 20km away as control. Levels of 16 USEPA priority Polycyclic Aromatic Hydrocarbons PAHs were determined using GC-FID. Source prediction analysis was also done. The study was in Niger Delta region, Nigeria from January to March and June to August 2012 in dry and wet seasons. Benzo(a)pyrene had highest total concentration of 3.302mg/kg and mean value of 1.651mg/kg in dry season soil samples. However, sediment samples had highest levels for total concentration of PAHs of 19.362mg/kg and mean of 4.840mg/kg for both dry and rainy seasons within Warri. PAHs concentration was higher in dry than rainy seasons for soil and sediment samples. Source prediction analysis revealed that PAHs in sediments for dry season were pyrolytic while rainy seasons were petrogenic sources. For soils, the dry season was mixed sources while the rainy season was petrogenic. / Environmental Science / M. Sc. (Environmental Science)

No description available.

No description available.

This thesis provides a mass conservation analysis of the Lower St. Johns River for the purpose of providing basis for future salinity transport modeling. The analysis provides an assessment of the continuous (CG) and discontinuous (DG) Galerkin finite element methods with respect to their mass conservation properties. The following thesis also presents a rigorous literature review pertaining to salinity transport in the Lower St. Johns River, from which this effort generates the data used to initialize and validate numerical simulations. Two research questions are posed and studied in this thesis: can a DG-based modeling approach produce mass conservative numerical solutions; and what are the flow interactions between the river and the marshes within the coastal region of the Lower St. Johns River? Reviewing the available data provides an initial perspective of the ecosystem. For this, salinity data are obtained and assembled for three modeling scenarios. Each scenario, High Extreme, Most Variable, and Low Extreme, is 30 days long (taken from year 1999) and represents a unique salinity regime in the Lower St. Johns River. Time-series of salinity data is collected at four stations in the lower and middle reaches of the Lower St. Johns River, which provides a vantage point for assessing longitudinal variation of salinity. As an aside, precipitation and evaporation data is presented for seven stations along the entire St. Johns River, which provides added insight into salinity transport in the river. A mass conservation analysis is conducted for the Lower St. Johns River. The analysis utilizes a segmentation of the Lower St. Johns River, which divides the domain into sections iv based on physical characteristics. Mass errors are then calculated for the CG and DG finite element methods to determine mass conservative abilities. Also, the flow interactions (i.e., volume exchange) between the river and marshes are evaluated through the use of tidal prisms. The CG- and DG- finite element methods are then tested in tidal simulation performance, which the results are then compared to observed tides and tidal currents at four stations within the lower portion of the Lower St. Johns River. Since the results show that the DG model outperforms the CG model, the DG model is used in the tidally driven salinity transport simulations. Using four stations within the lower and middle part of the Lower St. Johns River, simulated and observed water levels and salinity concentrations are compared.

No description available.

The impact of natural disasters is often exacerbated by a disparity between resources for relief and recovery. When the barrio of Punta Santiago in Puerto Rico was devastated by Hurricane Maria in September of 2017, many of its residents lived in the remains of their homes for over a year while they rebuilt from wind damage and flood waters that rose over 6 feet. As climate change leads to an even more constrained timeline for response with increasingly frequent and intense storms, the future of Punta Santiago and other coastal communities worldwide will necessitate strategies ranging from nature-based shore protection systems, coastal setbacks, and managed retreat. This thesis investigates the time disparate processes of disaster relief, recovery, and climate adaptation through the lens of their impact upon the interdependent identities of people and place as informed by theorists and designers including J.B. Jackson and Patrick Geddes. My approach works from the scale of the Antón Ruíz watershed to the delta to uncover the historical and contemporary processes that knit people in the region to the land. I identify commonalities in the immediate recovery needs and long-term resiliency of the community and ecosystems, and seek to support ongoing globally significant research of the rare coastal systems surrounding Punta Santiago. The proposed design, a causeway linking the coast to the hills, dovetails disaster relief and recovery with climate adaptation by providing a persistent connection that restores and reveals the dynamic coastal landscape. / Master of Landscape Architecture / Global warming is correlated with an increase in sea level rise, atmospheric moisture (water content in the air), and surface sea temperatures. The body of research around the complex interaction of these factors is growing, but current projections are that warmer seas will cause more intense hurricanes. Coastal communities, particularly those with fewer economic resources, bear the brunt of this trend and recovery is more difficult with each passing storm. After Hurricane Maria struck in September 2017, many residents of the barrio of Punta Santiago in Puerto Rico lived in the remains of their homes for over a year with little resources to rebuild from the severe wind damage and flood waters that rose over 6 feet. Recovery is still underway almost two years later. A sustainable way forward for Punta Santiago and other coastal communities worldwide necessitates strategies ranging from natural shore stabilization techniques like mangrove buffers and living reefs to restrictions on coastal development, and even the relocation of communities. This thesis investigates the time disparate processes of disaster relief, recovery, and climate adaptation through the lens of their impact upon the interdependent identities of people and place as informed by theorists and designers including J.B. Jackson and Patrick Geddes. My approach works from the scale of the Antón Ruíz watershed to the delta to uncover the historical and contemporary land use that knit people in the region to the land. I identify commonalities in the immediate recovery needs and long-term resiliency of the community and ecosystems, and seek to support ongoing globally significant research of the rare coastal systems surrounding Punta Santiago. The proposed design, a causeway linking the coast to the hills, dovetails disaster relief and recovery with climate adaptation by providing a persistent connection that restores and reveals the dynamic coastal landscape.

La question de recherche à la base de cette étude soulève le point de la nature paradoxale du canon de représentation égyptien qui démontre, simultanément, une certaine rigidité dans l’application de règles stylistiques et iconographiques établies, particulièrement dans l’art non commandité par l’État, et des preuves de transformation et d’intégration de motifs nouveaux. Partant de cette problématique, l’étude vise à identifier les mécanismes par lesquels ce canon permet, à la fois, l’innovation et le maintien d’une certaine tradition. L’approche est de nature double et consiste tout d’abord à identifier de grandes tendances et discontinuités stylistiques et iconographiques sur les bols de faïence du Moyen au Nouvel Empire. De plus, elle tente de déterminer si les transformations d’ordre sociopolitique et idéologique, survenant à ces périodes, peuvent être lues dans les variations stylistiques et iconographiques trouvées sur les bols de faïence. Après une description du champ conceptuel de la « représentation » en contexte égyptien, l’auteur effectue l’analyse iconographique exhaustive de ce qui constitue l’apport majeur de son étude, un corpus de 500 bols et fragments de faïence provenant de divers sites égyptiens du Moyen au Nouvel Empire. Les données ont été traitées par le biais de la méthode d’analyse iconologique proposée par Panofsky, qui lui permet de dévoiler un grand nombre de continuités et de transformations d’ordre stylistique et iconographique pour les différentes périodes. Plusieurs facteurs semblent avoir été à l’origine de ces transformations, dont la fluctuation entre un contexte de centralisation et de décentralisation politique de l’État, ainsi que l’intégration de motifs étrangers (proche-orientaux et égéens) résultant d’un contact accru entre l’Égypte et les régions voisines. De plus, les transformations idéologiques apportées par le règne d’Akhénaton et par la « contre-réforme » idéologique à la période ramesside, semblent avoir également contribué à des innovations au sein du canon, même si ce dernier maintient une certaine continuité légitimée par le pouvoir étatique. Le canon de représentation, devient ainsi une forme de langage dont l’État se sert et qui, parfois malgré lui, se transforme et fluctue selon les réalités des différentes périodes. / This study’s research question raises the issue of the paradoxical nature of the Egyptian canon of representation which shows, simultaneously, a certain rigidity in the application of established stylistic and iconographic rules, especially in non-state commissioned art, and evidence for the transformation and integration of new iconographical motifs. The study aims to identify the mechanisms by which the canon permits, at the same time, transformative processes and the maintenance of tradition. The approach is twofold and consists primarily in identifying trends and stylistic/iconographical discontinuities in the iconography found on the faience bowls from the Middle to the New Kingdoms. Furthermore, it aims to determine if the socio-political and ideological transformations taking place in these periods can be discerned in the stylistic and iconographical variations found on the bowls of the Middle to the New Kingdoms. The author discusses the theoretical model of “representation” in Egyptian context, followed by an analysis of what constitutes the major contribution of this study: an exhaustive iconographical analysis of 500 faience bowls and fragments originating from various Egyptian sites dating to the New Kingdom. The data was evaluated by means of the method of iconological analysis proposed by Panofsky, which permits the identification of a number of stylistic and iconographic continuities and changes for all periods. These transformations seem to be the result of a variety of factors, including fluctuations in the centralization and decentralization of the state, as well as the integration of foreign motifs (Near-Eastern and Aegean), which results from increased contacts between Egypt and its neighbouring regions. Furthermore, the ideological transformations taking place under Akhenaton’s reign and the ones resulting from the ideological “counter-reformation” occurring during the Ramessid period, equally seem to contribute to the changes in the representational canon, even though the latter maintained a certain continuity that was legitimized by the state. The canon thus emerges as a form of language used by the state, and sometimes despite it, which can fluctuate and be altered depending on the realities of the different periods.

Made available in DSpace on 2016-08-19T18:20:37Z (GMT). No. of bitstreams: 1 Carolina Mattosinho de Carvalho Alvite.pdf: 6763080 bytes, checksum: d171930fac0eadfa71fb881a91e48018 (MD5) Previous issue date: 2008-09-28 / INSTITUTO INTERNACIONAL DE EDUCAÇÃO DO BRASIL / The Brazilian north coast has the largest continuous area of mangroves on the planet and hosts large groups of manatees, aquatic mammal critically endangered. This research examines the efforts of fix point methodology of observation of manatees on relevant sites of occurrence, from data collected while on the beach in Guarapiranga (GUA), São José de Ribamar and on Ilha do Gato (IGA), Baía do Tubarão. This article discusses the application of population index for manatees in a ecological-environmental study on IGA (02°31'09, 81"S, 43°37'09,13" W), Mapari estuary, serving as a methodological basis to be replicated in other parts of the coast. From the application of index developed with data from fixed point and the characterization of the environmental area, the study provides evidence to infer the relative abundance of the population and it trends over the years, discussing aspects of spatial and temporal use of estuary. Was characterized: temperature, salinity, pH, conductivity, depth, current speed, tides fluctuations, rainfall, biomass of salt-marsh (Spartina alterniflora), and density of plants/seedlings of mangrove. The region showed a seasonal variation marked by two regimes of water, rain (January-July) and dry (August-December), with annual rainfall of 1,704mm. The oceanographic parameters ranged from tides: salinity (FLOOD=14.8; EBB=1.5), conductivity (FLOOD=27.1; EBB=6.3mS/cm), speed of current (FLOOD=46; EBB=88m/s). The tide height ranged from 0.0-5.4m. Biomass of S. alterniflora ranged from 860g/m2(RAIN) to 430g/m2(DRY) and density of plants/seedlings of 74ind/m2(RAIN) to 21ind/m2(DRY). Variations between rain/dry seasons influenced the availability of fresh water and food resources, important factors in the choice of areas for manatees. The estuary was shown with strong influence of daily tide fluctuations, reflecting changes in salinity, current speed, depth and access to plant resources by manatees. Between 2004/2007, manatees were monitored in 1241 days (GUA = 625, IGA = 616). The population analysis carried out in two sites of Maranhão indicated a trend of reducing population between 2004 and 2006, with stabilization between 2006 and 2007. The IGA had the highest relative abundance and showed to be important site of occurrence of manatees, which used as an area of reproduction, parental care, food and rest. IGA in the number of manatees seems to have relation with the seasons, being sighted in greater numbers in the rainy season. Variations during the tides also shown to influence the pattern of use of the IGA, and the manatees were more frequent in the tides ebb and flood. The main type of human activity in the IGA was not motorized boat and it had no negative influence on the occurrence of fish-horse. Knowledge about characteristics of coastal ecosystems is essential for development of appropriate conservation strategies for manatees in the Brazilian north coast. / O litoral norte do Brasil possui a maior área contínua de manguezais do planeta e abriga importantes grupos de peixes-bois-marinhos, mamífero aquático criticamente ameaçado de extinção. Esta pesquisa analisa o esforço da metodologia de observação de peixes-bois por meio de plataformas fixas em sítios de relevante ocorrência, a partir dos dados coletados simultaneamente na praia de Guarapiranga (GUA), São José de Ribamar, e na barra da Ilha do Gato (IGA), Baía do Tubarão. Também é discutida a aplicação de indicadores populacionais e ecológicos para peixes-bois em estudo de caso na barra da Ilha do Gato (02°31 09,81 S; 43°37 09,13 W), estuário do rio Mapari, servindo de base metodológica para ser replicada em outros pontos da costa. A partir da aplicação dos indicadores elaborados com os dados de ponto fixo e da caracterização ambiental da área, a pesquisa fornece elementos para inferir a abundância relativa da população e como esta se comporta ao longo dos anos, discutindo aspectos da utilização espacial e temporal do estuário. Para caracterização ambiental da IGA, foram levantados os seguintes parâmetros: temperatura (ar-água), salinidade, pH, condutividade, profundidade, velocidade de corrente, amplitude de marés, precipitação pluviométrica, biomassa de marisma (Spartina alterniflora), densidade de plântulas de mangue. A região mostrou uma variação sazonal do regime hidrológico: chuva (janeiro-julho) e seca (agosto-dezembro), com precipitação pluviométrica anual de 1704mm. Os parâmetros oceanográficos médios variaram entre as marés: salinidade (ENCH=14,8, VAZ=1,5), condutividade (ENCH=27,1, VAZ=6,3 mS/cm), velocidade de corrente (ENCH=46; VAZ=88 m/s). A altura da maré variou entre 0,0-5,4m. A biomassa de S. alterniflora variou de 860g/m2(chuva) a 430g/m2(seca) e a densidade de plântulas de 74 ind/m2(chuva) a 21 ind/m2(seca). As variações entre os períodos de seca e chuva influenciaram na disponibilidade de água doce e recursos vegetais, fatores determinantes na escolha de áreas pelos peixes-bois. O estuário mostrou-se com forte influência da variação diária nos regimes de maré, refletindo em mudanças na salinidade, velocidade de corrente, profundidade e acesso aos recursos vegetais pelos peixes-bois. Entre 2004/2007, os peixes-bois foram monitorados em 1.241 dias (GUA=625, IGA=616). As análises populacionais realizadas nos dois sítios do Maranhão indicaram uma tendência de redução populacional entre 2004 e 2006, com estabilização entre 2006 e 2007. A Ilha do Gato apresentou a maior abundância relativa e mostrou ser importante sítio de ocorrência de peixes-bois, sendo utilizada como área de reprodução, cuidado parental, alimentação e repouso. Na IGA o número de peixes-bois parece ter relação com as estações do ano, sendo avistados em maior número no período chuvoso. As variações nas fases de maré também mostraram ter influência no padrão de utilização da IGA, sendo que os peixesbois estiveram mais freqüentes nas marés vazantes e cheias. A ocorrência de embarcações não motorizadas foram a atividade humana com maior freqüência na IGA e não teve influência negativa na ocorrência dos peixes-bois. O conhecimento sobre as características dos ecossistemas costeiros é essencial para a elaboração de estratégias de conservação adequadas para o peixe-boi-marinho na região norte do Brasil.

La question de recherche à la base de cette étude soulève le point de la nature paradoxale du canon de représentation égyptien qui démontre, simultanément, une certaine rigidité dans l’application de règles stylistiques et iconographiques établies, particulièrement dans l’art non commandité par l’État, et des preuves de transformation et d’intégration de motifs nouveaux. Partant de cette problématique, l’étude vise à identifier les mécanismes par lesquels ce canon permet, à la fois, l’innovation et le maintien d’une certaine tradition. L’approche est de nature double et consiste tout d’abord à identifier de grandes tendances et discontinuités stylistiques et iconographiques sur les bols de faïence du Moyen au Nouvel Empire. De plus, elle tente de déterminer si les transformations d’ordre sociopolitique et idéologique, survenant à ces périodes, peuvent être lues dans les variations stylistiques et iconographiques trouvées sur les bols de faïence. Après une description du champ conceptuel de la « représentation » en contexte égyptien, l’auteur effectue l’analyse iconographique exhaustive de ce qui constitue l’apport majeur de son étude, un corpus de 500 bols et fragments de faïence provenant de divers sites égyptiens du Moyen au Nouvel Empire. Les données ont été traitées par le biais de la méthode d’analyse iconologique proposée par Panofsky, qui lui permet de dévoiler un grand nombre de continuités et de transformations d’ordre stylistique et iconographique pour les différentes périodes. Plusieurs facteurs semblent avoir été à l’origine de ces transformations, dont la fluctuation entre un contexte de centralisation et de décentralisation politique de l’État, ainsi que l’intégration de motifs étrangers (proche-orientaux et égéens) résultant d’un contact accru entre l’Égypte et les régions voisines. De plus, les transformations idéologiques apportées par le règne d’Akhénaton et par la « contre-réforme » idéologique à la période ramesside, semblent avoir également contribué à des innovations au sein du canon, même si ce dernier maintient une certaine continuité légitimée par le pouvoir étatique. Le canon de représentation, devient ainsi une forme de langage dont l’État se sert et qui, parfois malgré lui, se transforme et fluctue selon les réalités des différentes périodes. / This study’s research question raises the issue of the paradoxical nature of the Egyptian canon of representation which shows, simultaneously, a certain rigidity in the application of established stylistic and iconographic rules, especially in non-state commissioned art, and evidence for the transformation and integration of new iconographical motifs. The study aims to identify the mechanisms by which the canon permits, at the same time, transformative processes and the maintenance of tradition. The approach is twofold and consists primarily in identifying trends and stylistic/iconographical discontinuities in the iconography found on the faience bowls from the Middle to the New Kingdoms. Furthermore, it aims to determine if the socio-political and ideological transformations taking place in these periods can be discerned in the stylistic and iconographical variations found on the bowls of the Middle to the New Kingdoms. The author discusses the theoretical model of “representation” in Egyptian context, followed by an analysis of what constitutes the major contribution of this study: an exhaustive iconographical analysis of 500 faience bowls and fragments originating from various Egyptian sites dating to the New Kingdom. The data was evaluated by means of the method of iconological analysis proposed by Panofsky, which permits the identification of a number of stylistic and iconographic continuities and changes for all periods. These transformations seem to be the result of a variety of factors, including fluctuations in the centralization and decentralization of the state, as well as the integration of foreign motifs (Near-Eastern and Aegean), which results from increased contacts between Egypt and its neighbouring regions. Furthermore, the ideological transformations taking place under Akhenaton’s reign and the ones resulting from the ideological “counter-reformation” occurring during the Ramessid period, equally seem to contribute to the changes in the representational canon, even though the latter maintained a certain continuity that was legitimized by the state. The canon thus emerges as a form of language used by the state, and sometimes despite it, which can fluctuate and be altered depending on the realities of the different periods.

Zooplankton community structure (composition, diversity, dynamics and trophic relationships) of Mediterranian marshes, has been analysed by means of a size based approach. In temporary basins the shape of the biomass-size spectra is related to the hydrological cycle. Linear shape spectra are more frequent in flooding situations when nutrient input causes population growth of small-sized organisms, more than compensating for the effect of competitive interactions. During confinement conditions the scarcity of food would decrease zooplankton growth and increase intra- and interspecific interactions between zooplankton organisms which favour the greatest sizes thus leading to the appearance of curved shape spectra.Temporary and permanent basins have similar taxonomic composition but the latter have higher species diversity, a more simplified temporal pattern and a size distribution dominated mainly by smaller sizes. In permanents basins zooplankton growth is not only conditioned by the availability of resources but by the variable predation of planktivorous fish, so that the temporal variability of the spectra may also be a result of temporal differences in fish predation.Size diversity seems to be a better indicator of the degree of this community structure than species diversity. The tendency of size diversity to increase during succession makes it useful to discriminate between different succession stages, fact that is not achieved by analysing only species diversity since it is low both under large and frequent or small and rare disturbances. Amino acid composition differences found among stages of copepod species indicate a gradual change in diet during the life cycle of these copepods, which provide evidence of food niche partitioning during ontogeny, whereas Daphnia species show a relatively constant amino acid composition. There is a relationship between the degree of trophic niche overlap among stages of the different species and nutrient concentration. Copepods, which have low trophic niche overlap among stages are dominant in food-limited environments, probably because trophic niche partitioning during development allow them to reduce intraspecific competition between adults, juveniles and nauplii. Daphnia species are only dominant in water bodies or periods with high productivity, probably due to the high trophic niche overlap between juveniles and adults. These findings suggest that, in addition to the effect of interspecific competition, predation and abiotic factors, the intraspecific competition might play also an important role in structuring zooplankton assemblages. / L'estructura de la comunitat zooplanctònica dels Aiguamolls de l'Empordà, composició específica, dinàmica, diversitat i relacions tròfiques, s'ha estudiat a partir d'una aproximació basada en la mida. L'aproximació s'ha basat en la modelització de l'espectre de mida-biomassa de la comunitat zooplanctònica a partir de la distribució de Pareto. S'ha observat que la forma de l'espectre de mida-biomassa del zooplàncton canvia segons les condicions ambientals: en situacions d'entrada d'aigua són més freqüents els espectres lineals ja que les entrades de nutrients causen un creixement dels organismes de mida petita de manera que es sobrecompensa l'efecte de les interaccions competitives. Els espectres corbats són més freqüents en situacions de confinament quan els recursos són escassos i les interaccions ecològiques entre els organismes prenen més rellevància de manera que es veuen més afavorides les espècies de mida gran que les de mida petita. Les comunitats zooplanctòniques de les diferents llacunes de la maresma tenen una composició taxonòmica similar però una diversitat d'espècies, un patró estacional i una distribució de mides diferents. En el patró estacional de les llacunes temporànies es poden distingir sis situacions que estan condicionades per el cicle hidrològic i dominades per les següents espècies: Synchaeta spp, Diacyclops bicuspidatus, Eurytemora velox. Calanipeda aquae-dulcis, Cletocamptus confluens i Brachionus plicatilis. La llacuna permanent, tot i presentar una diversitat més alta que les temporànies, té un patró estacional més simple, amb només dues situacions: la situació de Synchaeta spp. i la de C. aquae-dulcis. Aquest patró estacional més reduït i una distribució de mides dominada principalment per organismes de mida petita s'explicarien per la pressió de depredació dels peixos en aquesta llacuna. Així, la variació en la forma de l'espectre de mida-biomassa de les comunitats zooplanctòniques de la llacuna permanent no està únicament relacionat amb el cicle higrològic sinó amb la pressió de depredació dels peixos.La distribució de Pareto es pot utilitzar per calcular un índex de diversitat de mides (μs'). En el cas de la comunitat de zooplàncton la diversitat de mides ha resultat ser un millor indicador del nivell d'estructuració que la diversitat d'espècies, els augments de la qual moltes vegades no són deguts a una elevada estructuració de la comunitat. La tendència a augmentar al llarg de la successió fa que la diversitat de mides pugui discriminar entre diferents estadis de la successió, en canvi això no es possible a partir de la diversitat d'espècies ja que pot assolir valors elevats tant en moments de pertorbacions elevades i freqüents com en moments de pertorbacions petites i escasses. En llacunes temporànies, valors alts de diversitat de mides coincideixen en períodes de dominància d'una espècie de calanoid, períodes que representen les situacions més estables en aquestes llacunes. L'anàlisi de la composició d'aminoàcids (AAC) ens demostra que les espècies de copèpodes dominants als Aiguamolls de l'Empordà mostren un canvi gradual en la seva composició bioquímica al llarg de la seva ontogènesi. Aquestes diferències en la AAC entre estadis no són degudes a diferències filogenètiques ni a les condicions ambientals, sinó a variacions en la dieta. Així, les diferents espècies de copèpodes mostren una repartició del nínxol tròfic entre els seus estadis de desenvolupament. Pel que fa a les espècies de dàfnids, mostren una AAC relativament constant durant el seu desenvolupament, fet que indicaria que tot els estadis s'alimenten del mateix recurs, és a dir, que juvenils i adults mostren un solapament del nínxol tròfic. La relació trobada entre la concentració de nutrients de les llacunes i el grau de solapament entre estadis de les espècies dominants mostra que la repartició del nínxol tròfic entre joves i adults és un possible mecanisme per tal d'evitar la competència intraespecífica. Els copèpodes, que tenen un baix solapament entre estadis, dominen en ambients on el recurs és limitat ja que la repartició del nínxol tròfic durant el desenvolupament els permet reduir la competència per l'aliment entre estadis. En les espècies de dàfnids, l'elevat solapament entre joves i adults els restringeix en llacunes o períodes amb elevada productivitat per tal d'evitar la competència intraespecífica. Així doncs, la competència intraespecífica juga un paper important a l'hora d'estructurar la comunitat de zooplàncton, juntament amb els dos altres factors que sovint són citats, la depredació i la competència interspecífica.