The aim of this study was to evaluate the nutritional value of algae and zooplankton grown in an algal integrated ponding system for poeciliids. The available information on the nutritional requirements of poeciliids was compared with a proximate analysis of the algae and zooplankton. The effluent grown algae and zooplankton had a crude protein value of 41.47 ± 0.2% and 36.84 ± 0.3%, a lipid content of 4.8 ±. 0.4% and 11.1 ± 0.8% and a carbohydrate content of 35.13 ± 0.8% and 31.06 ± 0.6% respectively. These values compared favourably with those of the known nutritional requirements of poeciliids. To test if the nutritional value of the algae and zooplankton in the AlPS was constant, the species composition of the algae and the crude protein content of the algae and zooplankton in the high rate oxidation ponds were measured monthly and bi-weekly for a year respectively. The species composition remained fairly stable for the duration of the experiment and the average protein composition of the algae and zooplankton was 43.4 ± 4.4% and 38.6 ±2.8% respectively. This indicated that the algae and zooplankton in the AlPS provided high protein biomass through the year. The quality of the effluent grown algal and zooplankton biomass was evaluated by analysing their amino acid composition and comparing it with the amino acid composition of the body tissue of X. helleri. With respect to the amino acid composition of the body tissue of X. helleri, the amino acid profile of the algae had a 69% and the zooplankton a 63% similarity. The quality of the pure algal and zooplankton protein was also tested biologically, by feeding them directly to poeciliids during a ten week growth trial. The algae and zooplankton diets did not result in adequate growth compared to poeciliids which were fed a formulated control diet. The initial growth trial also evaluated the effect of processing on the chemical composition of the algae and its biological effect on fish fed with it. There were no significant differences in the chemical composition of fresh and sun dried algae and this was reflected in the growth rates of the fish which did not differ significantly. Freeze dried algae had a lower crude protein content than fresh and sun dried algae and a poorer amino acid composition. Fish fed freeze dried algae exhibited poorer growth and survival in comparison to the other treatments. The gut transit times of X. helleri and the gastric evacuation times of poeciliids were determined using colour dyes incorporated in the diet and by sacrificing fish at predetermined intervals after feeding respectively. The gut transit time of X. helleri fed a sun dried algal diet and a formulated diet was 225 ± 8.55 minutes and 261.93 ± 10.86 minutes respectively. The gastric evacuation times of X. helleri, P. reticu/ata and P. velifera were 7, 9 and 8 hours respectively. Since the maximum amount of food in the hindgut after feeding was detemined to be 3, 5 and 3 hours in X. helleri, P. reticulata and P. velifera respectively, fish were sacrificed at these times in the digestibility study. The digestibility of sun dried algae was determined using 1 % chromic oxide as an internal marker in the algae. The apparent crude protein digestibility of sun dried effluent grown algae ranged from 65%-75% in the three poeciliid species. Based on the results of the chemical and biological analysis of the algae and zooplankton, conventional diets incorporating algae at 5% and 20% protein inclusion levels were formulated. These diets and a treatment in which zooplankton, reared in the AlPS were fed as a dietary supplement to a formulated diet were fed to poeciliids for twelve weeks. No significant differences in the growth of poeciliids fed any of the test diets were observed. It was concluded that the algae could be incorporated into poeciliid formulated diets up to level of 20% protein inclusion without any negative effect on the growth of the fish. The chemical and biological evaluation of the algae suggested that it had a similar nutritional quality to soyabean meal. Poeciliid growth was not enhanced with a zooplankton supplement, however a possible low feeding rate by poeciliids on the zooplankton as a result of their small size may have affected the result. The colour enhancement potential of effluent grown algae and zooplankton was evaluated biologically in ten and twelve week growth trials using visual observation (31 people) and by using a chromameter. While pure, sun dried algae significantly enhanced the colour of P. reticulata, no significant differences in the colour of poeciliids were observed or recorded when fish were fed diets incorporating sun dried algae up to levels of 20% protein inclusion. The effect of effluent grown algae and zooplankton on poeciliid health was also tested biologically in the ten and twelve week growth trials. The high mortalities (75%-84%) recorded for X. hel/eri when fed the pure algal and zooplankton diets were considered to be as a result of the nutritional inadequacy of the diets since there were significantly less mortalities in fish fed the formulated control diet and 63% of the fish that died during the course of the trial were emaciated. In addition, fewer mortalities (10%-40%) were recorded in X. hel/eri fed the nutritionally adequate formulated diets in the twelve week growth trial. No symptoms of disease were recorded in the twelve week growth trial and the algae was considered to have no toxicological or pathological effects on poeciliids. Centrifugation, sand filtration, sedimentation, microstraining and biological harvest were evaluated as methods of small scale algal harvest from the high rate oxidation ponds. Algae could be harvested most efficiently with little associated labour by sedimentation (without flocculating agents) and by microstraining with 60IJm mesh. Effluent grown algae can replace conventional feed ingredients up to a level of 20% protein inclusion without negatively effecting the growth, colour, health or survival of poeciliids.

The trophodynamic implications of reduced freshwater inflow on the zooplankton of eastern Cape estuaries was investigated by a comparison of the community composition and standing stocks, grazing rates and food resources of zooplankton in two systems, the Kariega and the Great Fish estuaries, which are subject to contrasting freshwater inflow. The climate of South Africa is semi-arid, and the low rainfall, coupled with high evaporative loss, result in the region having one of the lowest conversions of rainfall to run-off in the world. In addition, many of the major rivers are extensively impounded, consequently, estuaries often experience prolonged periods of zero or reduced freshwater inflow. The amount of freshwater available for estuarine management in the future is expected to decline as the demand for domestic, agricultural and industrial use increases. The influence of climate, tidal amplitude and wave action are essentially constant, consequently, the individual characteristics of an estuary are determined largely by the indirect influences of catchment size and regulation. Estuaries along the eastern Cape coast range from negative hypersaline systems, to positive systems in which a salinity gradient is well established. The Kariega estuary is a homogeneous marine estuary as a result of minimal freshwater inflow, whereas the Great Fish estuary receives sustained freshwater inflow and is partially-stratified. The quality and quantity of particulate food resources for suspension-feeders depended to a large extent on the allochthonous import of material associated with freshwater inflow. Nutrients, rather than light penetration of the watercolumn are the major factor limiting phytoplankton standing stocks. In the Kariega estuary, phytoplankton standing stocks were low (up to 1.0 μg l⁻¹) and the estuary is classified as oligotrophic. Correlation analyses indicated that lower quality detritus, originating from fringing macrophytes, may contribute substantially to suspended particulate organic material. Phytoplankton food resources were considerably higher in the Great Fish estuary (up to 21.8 μg ⁻¹) which is classified as mesotrophic/eutrophic, and correlation analyses indicated that phytoplankton comprised the dominant fraction of the particulate organic material. Although this suggested that the organic material was of a higher quality, the seston was "masked" by a higher suspended inorganic load. Consequently, the organic fraction comprised between 13 and 22% of total particulate material in the Great Fish estuary, compared with between 20 and 39% in the Kariega estuary. Food resources demonstrated a fairly uniform distribution along the length of the Kariega estuary and exhibited a slight seasonal increase during warmer months. By contrast, the point source influence of freshwater inflow resulted in a spatial gradient of food resources in the Great Fish estuary with higher values recorded towards the upper reaches. There was evidence that higher concentrations of particulate material in the upper reaches are also a consequence of hydrodynamic trapping. There was no marked seasonal pattern in the availability of food resources which were generally elevated in response to sporadic pulses of freshwater inflow. Tidal currents were responsible for elevating suspended food resources by re-suspension of material from the sediments. This effect was probably of greater importance in the Kariega estuary where food resources were generally limiting. In the Kariega estuary, the zooplankton community was dominated by calanoid copepods of the genera Acartia and Pseudodiaptomus. However, in the Great Fish estuary, the community was dominated by the mysid Mesopodopsis siabberi, and the calanoid P. hessei. Community biomass generally reflected the trophic status of the estuary. The mean seasonal biomass recorded in the Kariega estuary was 38 mg m⁻³ compared with 1597 mg m⁻³ in the Great Fish estuary. Greater spatial variability in community biomass was evident in the Great Fish estuary, partly in response to the food resource gradient, but also due to the inability of the mysid shrimps, which dominated the community biomass, to penetrate the lower salinity water of the upper reaches. Zooplankton in the Kariega estuary demonstrated a seasonal pattern of abundance whereas in the Great Fish estuary, community biomass was elevated in response to sporadic pulses of freshwater inflow. Grazing rates, measured in situ using a modified Gliwicz-Haney chamber, indicated that the zooplankton communities were capable of "clearing" substantial proportions of the watercolumn at certain times of the year. The pattern of grazing pressure over a diel cycle was examined in relation to the diel vertical migration movements of the zooplankton. Higher nighttime grazing rates were generally associated with the greater abundance of zooplankton resulting from the movement of zooplankton into the watercolumn after dusk, and their return to the sediments at dawn. Seasonal estimates of diel grazing pressure, extrapolated from daytime and nighttime feeding rates, indicated that the zooplankton "cleared" up to 40% of the watercolumn in a day in the Kariega estuary, and up to 120% d⁻¹ in the Great Fish estuary. However, values of around 25% d⁻¹ in the Kariega estuary, and 50 to 80% d⁻¹ in the Great Fish estuary, were not uncommon. Multiple regression analyses were used in an attempt to explain the influence of environmental factors on the variation in in situ grazing rates. These attempts were largely unsuccessful and the possible reasons, as well as recommended improvements to the methods used, are discussed. Seston concentration in the estuaries was highly variable as a result of the effects of tidal re-suspension and freshwater inflow. Consequently, further laboratory-based experiments were carried out to examine the influence of seston concentration on the filtration rates of the dominant calanoid copepods. Results indicated that some of the unexplained variability in the community filtration rates may be attributed to differences in species-specific response to changes in seston concentration.

Trophodynamics of carnivorous zooplankton in the region of the Subtropical Convergence (STC) in the Indian sector of the Southern Ocean was investigated during austral autumn (April 2007) as part of the first cruise of the Southern Ocean Ecosystem Variability Study. Within the region of the study, the STC was well defined by the 14°C surface isotherm which separated the Agulhas Return Current and Subtropical water in the north from Sub-Antarctic waters to the south. Total average abundance (3.89 ± 5.46ind 100m-3) and biomass (0.14 ± 0.27mg Dwt 100m-3) of carnivorous zooplankton south of the front were significantly higher than the total average abundance (1.33 ± 1.81ind 100m-3) and biomass (0.03 ± 0.05mg Dwt 100m-3) north of the front (p<0.001). There were no significant correlations between the selected physico-chemical (temperature and salinity) and the biological (mesozooplankton abundance and biomass) variables and the total abundance and biomass of the carnivorous zooplankton during the investigation (p>0.05 in all cases). There was no evidence of enhanced biomass and abundance values at stations occupied in the immediate vicinity of the front. Total average carnivorous zooplankton abundance was dominated by chaetognaths (Eukrohnia hamata Möbius 1875, Sagitta gazellae Ritler-Záhony 1909 and S. zetesios Fowler 1905) and euphausiids (Nematoscelis megalops Sars 1883, Euphausia longirostris Hansen 1908 and E. spinifera Sars 1883), which contributed up to 86.58 ± 32.91% of the total counts. The total average biomass was dominated by euphausiids and amphipods (Themisto gaudichaudii Guérin-Méneville 1825, Phronima sedentaria Forsskål 1775 and Vibilia armata Bovallius 1887) which contributed up to 71.45 ± 34.85% of the total counts. In general the populations of both the euphausiids and amphipods were dominated by females while the chaetognaths were dominated by juveniles. Numerical analysis identified two major zooplankton groupings within the survey area which did not coincide with the water masses within the survey area. The SIMPER procedure of the PRIMER package indicated differences between the groups were mainly attributed to changes in the abundance of the numerically dominant species rather than the presence or absence of individual species. The absence of any significant spatial patterns in the distribution of the carnivorous zooplankton suggests that the STC did not act as a biogeographical barrier during the present study. The mean feeding rates of the chaetognaths E. hamata, S. gazellae and S. zetesios were 1.82 ± 0.85prey d-1, 3.63 ± 2.08prey d-1 and 2.18 ± 0.59prey d-1, respectively. These rates correspond to a combined predation impact equivalent to <5% of the mesozooplankton standing stock or <10% of the mesozooplankton secondary production. Mesozooplankton, comprising mainly copepods was the dominant prey in the guts of the three chaetognath species. Total predation impact of the euphausiids, chaetognaths and amphipods, estimated using published daily ration data, on the mesozooplankton standing stock and secondary production ranged from 0.01% to 1.53% and from 0.03% to 30.54%, respectively. Among the carnivorous zooplankton, chaetognaths were generally identified as the dominant predators of mesozooplankton. Low predation impact of selected carnivorous zooplankton suggested that these organisms contributed little to the vertical carbon flux within the region of investigation during the study.

The global movement of aquatic non-indigenous species can have severe ecological, environmental and economic impacts emphasizing the need to identify potential invaders and transport pathways. Initial transport is arguably the most important stage of the invasion process owing to its role in selectively determining potential invasion candidates. This study characterizes a well defined human-mediated dispersal mechanism, ballast water transport, as a vector for the introduction of non-indigenous zooplankton. Ballast water exchange in the open ocean is the most widely adopted practice for reducing the threat of aquatic invasions and is mandatory for most foreign vessels intending to release ballast in Canadian waters. Ships entering Canadian ports are categorized into the following three shipping classes based on current regulations: overseas vessels carrying exchanged ballast water, intra-coastal vessels carrying exchanged ballast water or intra-coastal vessels carrying un-exchanged ballast water. This study characterizes zooplankton communities associated with each of these shipping classes sampled from ports on Canada’s Pacific coast, Atlantic coast and the Great Lakes Basin. Ballast water samples were collected and analyzed from 77 vessels between 2006 - 2007. The ballast water environment was found to be diverse, with over 193 zooplankton taxa, 71 of which were non-indigenous to their receiving environments. Intracoastal vessels containing un-exchanged coastal water transported the greatest density of non-indigenous zooplankton into Canadian ports. Total zooplankton density was found to be negatively correlated with ballast water age The absence of mandatory ballast water exchange and the younger ballast water age of coastal un-exchanged vessels is likely responsible for the higher density of non-indigenous zooplankton in intracoastal un-exchanged vessels. Propagule pressure, invasion history and environmental suitability are all useful in evaluating invasion potential and all suggest that intracoastal un-exchanged vessels pose the greatest invasion threat to Canadian aquatic ecosystems. In conclusion, although the risk of primary introductions from overseas ports may have been reduced through open-ocean exchange of ballast water, secondary introductions from previously invaded ports in North America may be the primary threat to Canadian aquatic ecosystems via this transport vector. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Copepods live in a nutritionally dilute environment, experiencing temporal and spatial variations in food supply which differ in magnitude and predictability. Understanding the mechanisms by which organisms deal with changes in their food is a primary concern in elucidating the nutritional ecology of zooplankton and the role of food in structuring zooplankton communities. In this thesis, I examine changes in behavior, morphology, and physiology of two species of calanoid copepods (Diaptomus kenai and D. leptopus) in response to variation in food composition and density. In Chapter Two, I present a study of population-level responses to variation in food composition and quality, using fertilization techniques to generate a range of phytoplankton communities in field enclosures. The phytoplankton assemblages studied supported copepod populations which differed in such attributes as population size, reproduction, and body size. The most striking finding of this study was the occurrence of two co-existing size classes of D. kenai, the abundance and clutch size of which varied among the enclosures, suggesting differences between the two classes in their ability to utilize the different phytoplankton communities. Chapter Three investigates patterns of lipid storage in response to changes in food supply. I concluded that lipid stores were affected by species composition of the phytoplankton food and the two copepod species differed in their sensitivity to differences in cell chemistry. Chapter Four investigates behavioral responses of the two size classes of D. kenai to changes in food composition and abundance. Subtle differences in feeding behavior suggest that the two sizes differ in their utilization of available food. These results demonstrate that D. kenai and D. leptopus are capable of responding to changes in their food supply through modifications of their behavior, morphology, and physiology over a range of magnitudes and time scales. There can be very subtle changes in feeding behavior or very pronounced changes in size structure. Responses occur over time scales ranging from hours to days to seasons. These results also bring into question the utility of models generated under laboratory conditions in predicting behaviors or dynamics of copepod populations and communities in nature. / Science, Faculty of / Zoology, Department of / Graduate

Understanding the impact which grazers have on their prey is of vital importance in understanding how aquatic ecosystems function. In an attempt to contribute to this understanding, this study examined, at three levels, the effects of zooplankton on phytoplankton biomass in Placid Lake in summer. Examination of selective feeding by the major herbivorous zooplankton species in in situ enclosures revealed that single phytoplankton cells in the range of 6-20 μm long were the preferred food of these organisms. Colonial algae, when dominated by the cyanophyte Merismopedia, did not appear to be grazed. The effect of zooplankton biomass on phytoplankton biomass was examined in in situ enclosures. Generally, phytoplankton biomass decreased only in enclosures where initial zooplankton biomass was very low or very high. A simple model based on the classical logistic model of predator-prey interactions was developed to explain events in the enclosures. I concluded that in summer, Placid Lake phytoplankton depend on nutrients remineralized by zooplankton for growth. Grazing appears to be an important regulating mechanism of the phytoplankton standing crop in the spring but not summer. A third level of study involved examination of the responses of phytoplankton to lake perturbation, namely removal of zooplankton, compared to plankton patterns in previous and subsequent years. In years lacking zooplankton manipulation, major increases in zooplankton biomass in mid spring were followed by phytoplankton biomass increases in late spring. During the first harvesting season, July and August 1979, a 50% reduction in zooplankton biomass was obtained. An enormous bloom of the inedible Merismopedia developed. I hypothesized that removal of zooplankton caused a shortage of available biologically reactive nitrogen which became limiting to eukaryotic phytoplankton, allowing Merismopedia, a blue-green alga which may be able to fix nitrogen, to thrive. In summer, the positive effect of zooplankton on phytoplankton via nutrient remineralization appeared to be more significant than the negative effect of grazing. During the second harvesting season, May, June, and July 1980, no decrease in zooplankton biomass was apparent. Instead of the usual pattern of zooplankton biomass increase preceeding the phytoplankton biomass increase, both increases occurred simultaneously. I concluded that harvesting delayed the rise in zooplankton biomass and decreased the grazing pressure on phytoplankton, allowing it to peak earlier. Grazing may thus be significant in spring in slowing phytoplankton growth. Seasonal variations were introduced to the model for the enclosure experiments to help understand the normal plankton patterns in Placid Lake. The time lag between maximum solar radiation and lake temperature, and the effects of these two physical parameters on phytoplankton and zooplankton growth appear to be instrumental in establishing the pattern of plankton biomass dynamics observed in Placid Lake. / Science, Faculty of / Zoology, Department of / Graduate

Submitted by Caroline Falcao (caroline.rfalcao@ufpe.br) on 2017-06-29T17:35:04Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) 2011-Dissertação-TiagoNunes.pdf: 14422947 bytes, checksum: c5fe4454b1a2c027cf01d48b6015c9ca (MD5) / Made available in DSpace on 2017-06-29T17:35:04Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) 2011-Dissertação-TiagoNunes.pdf: 14422947 bytes, checksum: c5fe4454b1a2c027cf01d48b6015c9ca (MD5) Previous issue date: 2011-02-28 / Os anfípodos zooplanctônicossão componentes significativos das comunidades epi e mesopelágicas. Ocupam nichos ecológicos diversificados e, em algumas regiões frias, dominam a biomassa planctônica, constituindo os principais itens alimentares depeixes e baleias planctófagos. Como dados sobre composição específica e variabilidade geográfica ainda são escassos especialmente para o oceano Atlântico Sul Ocidental, objetivou-se levantar a composição dos Amphipodapresentes emáguas oceânicas da Zona Econômica Exclusiva (ZEE) do Nordeste do Brasil, contribuindo para o conhecimento taxonômico de distribuição horizontal. Duas hipóteses foram testadas:1) possuem alta diversidade na área, constituindo uma comunidade complexa, porém, pouco abundante; 2) há espécies que ocorrem exclusivamente na região, em relação às demais águas brasileiras. Um total de 43 amostras de macrozooplâncton foi analisado,amostras essas coletadas entre junho e julho de 1998 nas áreas: Oceânica Este (OE), Arquipélago São Pedro e São Paulo (ASPSP) e Cadeia Rocas/Noronha (CRN), parte integrante do Projeto REVIZEE Score NE-III. As amostras foram obtidas no estrato de0 a200m através de arrastos oblíquos, com rede de náilon do tipo bongo, com abertura de malha de 300μme 500μmdurante 15 minutos,acoplada com fluxômetro digital. Para este trabalho foi utilizado o material retido na malha de 300μm. Dados de temperatura e salinidade foram igualmente aferidos. O material biológico foi fixado a bordo, emuma solução de formaldeído a 4% neutralizado com tetraborato de sódio. Os indivíduos foram separados, dissecados e identificados até a menor unidade taxonômica possível. Observou-se uma densidade máxima de 1,92 org.m-3na E111 (ASPSP), e uma mínima de 0,175 org.m-3na E143 (OE). Foram identificadas 68 espécies, sendo 5 da subordem Gammaridea e 63 da Hyperiidea, além de cinco instantes de associação com organismos gelatinosos. Eupronoe intermedia, Hyperietta vosseleri, Anchylomera blossevillei,Phronimella elongata,Lycaeopsis zamboangaee Primno latreilleiforam consideradas muito frequentes, sendo as quatro primeiras aquelas que se sobressaíram em abundância (12,6%; 21,4%; 11,5%; 10,2%, respectivamente), consideradas pouco abundantes, e todas as outras, raras. O ASPSP foi a área que apresentou maior diversidade e equitabilidade (4,248 bits.ind-1e E= 0,761). Segue-se a elea CRN (3,878 bits.ind-1e E= 0,744) e a OE (3,766 bits.ind-1e E= 0,654). Esses valores expressam uma altaequitabilidade e diversidade para a área estudada, quando comparados a valores encontrados na literatura para outras áreas marinhas do Brasil e do mundo; a primeira, expressando uma boa distribuição dos organismos ao longo da coluna d’água, e a segunda, corroborando a hipótese de que os anfípodos zooplanctônicos apresentam, da zona nerítica em direção à oceânica, uma diminuição na densidade e aumento na diversidade. Este estudo contribui ainda com sete novas ocorrências para o Nordeste do Brasil e duas para o Atlântico Sul Ocidental. / Zooplanktonic amphipods are significant components of the epi-and mesopelagic communities. They occupy diverse ecological niches and, in some cold regions, dominate the plankton biomass, constituting the food bank for fish and plankton whales. Given the data on species composition and geographic variability are scarce, especially for the South Atlantic Ocean, the main goal of thisdissertation was to register the composition of crustaceans found in ocean waters of the Exclusive Economic Zone (EEZ) of the Northeast of Brazil, contributing to the knowledge of the taxonomy and biogeography of this group. Two hypothesis were tested: (1) the diversity of zooplanktonic amphipods at this area is high, representing a complex but not abundant community; (2) there are exclusive species at the region level in comparison to other Brazilian marine areas. I analyzed 43 samples of macrozooplankton collected between June and July 1998 in: Oceânica Este (OE), São Pedro and São Paulo archipelagos (SP/SP) and Cadeia Rocas/Noronha (CRN). All samples were obtained in a depth between 0 e 200m by through oblique hauls lasting 15 minutes with a nylon mesh-type bong, with the gap between 300μm mesh coupled with digital flowmeter. Biological material was fixed aboard with formaldehyde 4% neutralized with sodium tetraborate. Individuals were dissected and identified at the lowest taxonomic level it was possible. It was observed the maximum density of 1,92 org.m-3at E111 (SP/SP), and the minimum density of 0,175 org.m-3at E143 (OE). I identified 68species: 5 fromthe sub-order Gammaridea and 63 from the sub-order Hyperiidea; five associations with gelatinous zooplankton were also found. Eupronoe intermedia, Hyperietta vosseleri, Anchylomera blossevillei,Phronimella elongata,Lycaeopsis zamboangaeand Primno latreilleiwere considered frequent species. Among them, the first four species were also considered not abundant (12,6%; 21,4%; 11,5%; 10,2%, respectively).SP/SP was the area with the highest diversity and evenness(4,248 bits.ind-1; E= 0,761), followed by CRN (3,878 bits.ind-1; E= 0,744) and OE (3,766 bits.ind-1; E= 0,654). Thesevalues expressahigh evennessand diversityin the studyareawhen compared tovalues foundin the literature forothers Brazilianand globalmarine areas. Evenness results expressingagooddistribution of organismsthroughout thewater column; and diversity values are supporting the hypothesisthat zooplanktonic amphipodsexhibita decreasein the density andincreasein the diversity, from theneriticzonetoward theoceanic zone. Seven species are new register for the Northeastern region of Brazil and other two species, for Western South Atlantic (also exclusively occurring at Northeastern region).

Zooplankton is crucial for lake ecosystems as it is an important component in most of the food webs of these ecosystems. However, environmental changes have caused reductions in ecosystems nutrients and stoichiometry, which directly affects phytoplankton’s development and quality. Studies were carried out in 33 different lakes throughout Sweden, divided into 4 regions (Abisko, Jämtland, Västerbotten and Värmland) to assess whether differences in environmental characteristics induced differences in phytoplankton abundance and zooplankton communities. Using data from 3 different seasons of the year, I found that zooplankton composition differed between northern and southern regions, and greater differences were found between the mountain regions than between the boreal regions. Dissolved inorganic N (DIN) and dissolved inorganic N to total P ratio (DIN:TP) concentrations were lower in northern regions than in southern regions. Phytoplankton biomass increased with dissolved organic carbon (DOC), likely through the positive effects of DOC on overall nutrient availability. DOC concentrations were higher in boreal regions than in mountain regions, as also happens with chlorophyll-a. Positive correlations between DOC and 3 different zooplankton genera were proven, whereas 3 different zooplankton taxa were correlated with DIN:TP (two negatively and one positively). Lakes with lower DIN:TP ratios had higher abundances of calanoids, which were the major contributor of the dissimilarity in zooplankton composition among the regions. Therefore, the DIN:TP ratio possibly has stronger effects than DOC on zooplankton composition in Swedish oligotrophic lakes. But further increases in DOC concentrations will likely reduce the differences in zooplankton composition caused by the declines in lake DIN:TP observed in this study.

As ocean temperatures continue to rise, the effect of temperature on marine organisms becomes highly relevant. The Red Sea is the warmest sea and is rapidly warming with current surface temperatures (28 – 34 °C) already exceeding those of most tropical systems. This has major consequences for organisms that may already find themselves at their thermal limits. The aim of this project was to define the thermal limits and thresholds of certain Red Sea species. Firstly, to better understand the thermal regimes of the Red Sea, we looked at decadal trends in maximum sea surface temperature across the basin. Then, we tested the thermal capacities of Red Sea mangroves and zooplankton, two key ecological groups, by performing thermal stress experiments in the laboratory. We found that the Red Sea basin is warming faster than the global average (0.17 °C decade-1), the thermal limit of mangrove propagules is between 33 and 35 °C, and the limits among the most common zooplankton groups range from 30 to 36 °C. This project gives us a better understanding of how organisms respond to extreme temperatures and how they may be affected in a future, warmer, ocean.

Zooplankton is crucial for lake ecosystems as it is an important component in most of the food webs of these ecosystems. However, environmental changes have caused reductions in ecosystems nutrients and stoichiometry, which directly affects phytoplankton’s development and quality. Studies were carried out in 33 different lakes throughout Sweden, divided into 4 regions (Abisko, Jämtland, Västerbotten and Värmland) to assess whether differences in environmental characteristics induced differences in phytoplankton abundance and zooplankton communities. Using data from 3 different seasons of the year, I found that zooplankton composition differed between northern and southern regions, and greater differences were found between the mountain regions than between the boreal regions. Dissolved inorganic N (DIN) and dissolved inorganic N to total P ratio (DIN:TP) concentrations were lower in northern regions than in southern regions. Phytoplankton biomass increased with dissolved organic carbon (DOC), likely through the positive effects of DOC on overall nutrient availability. DOC concentrations were higher in boreal regions than in mountain regions, as also happens with chlorophyll-a. Positive correlations between DOC and 3 different zooplankton genera were proven, whereas 3 different zooplankton taxa were correlated with DIN:TP (two negatively and one positively). Lakes with lower DIN:TP ratios had higher abundances of calanoids, which were the major contributor of the dissimilarity in zooplankton composition among the regions. Therefore, the DIN:TP ratio possibly has stronger effects than DOC on zooplankton composition in Swedish oligotrophic lakes. But further increases in DOC concentrations will likely reduce the differences in zooplankton composition caused by the declines in lake DIN:TP observed in this study.