This study aimed to investigate the feeding behaviour of the calanoid copepod, Pseudodiaptomus hessei, particularly whether it prefers to feed on a planktonic or benthic food source. The effect of different microalgae species on the feeding preference, ingestion, and gut evacuation rate were investigated. Two microalgae species (Isochrysis galbana and Tetraselmis suecica) were used, to test gut fullness and gut evacuation of P. hessei. The copepods were starved for 6 h and allowed to feed on monalgae diets, I .galbana and T. suecica, and a 1:1 binary diet mixture of T. suecica and I. galbana. The gut fullness and gut evacuation rates were determined by observing under the dissecting microscope and gut content percentage was recorded (as 0, 25, 50, 75 or 100 percent) along with copepod sex. Copepods that feed on T. suecica fill their gut after 30 min, while those that feed on I. galbana do so after 40 min. There was a significant difference (p= 0.02) between sexes with males filling their gut faster than females. However, copepods that fed on I. galbana evacuated their gut content completely after 30 min, while those fed on T suecica evacuated theirs after 40 min. There was no difference between males and females for gut evacuation. Even though there was high gut fullness rate when P. hessei was feeding on T. suecica, I. galbana is recommended as the best mono-algae diet to culture P. hessei. The feeding behaviour of P. hessei was investigated, as to whether it prefers to feed on a planktonic or benthic food source. Copepods were starved for 3 h and then allowed to feed on two microalgae species (I. galbana and T. suecica), one presented as a benthic and other as planktonic. Controls included swapping the modes of presentation for each algae species. Ingested microalgae species were quantified using real-time PCR, with threshold cycles interpreted as relative abundance ratio (planktonic microalgae divided by benthic microalgae species). Pseudodiaptomus hessei preferred to feed on planktonic food sources initially as there was a difference between planktonic and benthic ingested food (p=0.026). Copepods shifted from planktonic to benthic food sources after 80 min of feeding planktonically. Planktonic food sources were the preferred choice for P. hessei regardless of microalgae species offered. The results from this study also confirm that P. hessei feed on a benthic food source during the day under culture conditions. This information can be used as baseline information for aquaculturists to rear the species as live feed for marine fish larvae.

Orientador : Prof. Dr. José Guilherme Bersano Filho / Dissertação (mestrado) - Universidade Federal do Paraná, Setor de Ciências da Terra, Programa de Pós-Graduação em Sistemas Costeiros e Oceânicos. Defesa: Pontal do Paraná, 26/03/2015 / Inclui referências : f. 41-47 / Resumo: A estrutura e dinâmica das populações biológicas em estuários, especialmente no que se refere à comunidade planctônica, é reflexo da elevada variabilidade espaçotemporal de habitats. Organismos zooplanctônicos respondem rapidamente a mudanças nos parâmetros abióticos e bióticos do sistema, sendo considerados potenciais bioindicadores de alterações ambientais. O Complexo Estuarino de Paranaguá (CEP) está entre os principais ecossistemas costeiros da região sul-sudeste do Brasil, abrigando áreas de planície costeira, manguezais, marismas e Mata Atlântica. Apesar de sua importância nos processos ecológicos, a atual dinâmica da comunidade zooplanctônica na região é pouco conhecida. Este trabalho tem como objetivo descrever a variabilidade zooplanctônica no CEP, com base em dados de composição e abundância obtidos durante os períodos de verão e inverno de 2012 e 2013, em relação a mudanças ambientais associadas à variação climática sazonal. Para tal, as coletas foram realizadas através de arrastos oblíquos com rede cilíndrico-cônica (0,5 m de boca e 200 ?m de malha) ao longo de 37 pontos distribuídos no CEP, totalizando 148 amostras. Parâmetros ambientais, tais como temperatura da água e salinidade, foram coletados simultaneamente e dados atmosféricos foram obtidos a partir de estações meteorológicas da região. As variações de abundância e composição zooplanctônicas e suas relações com as condições hidrológicas foram avaliadas a partir de técnicas estatísticas de análise multivariada e os resultados indicaram diferenças significativas entre as comunidades. Foram detectados dois agrupamentos principais correspondentes às assembleias de verão e de inverno, separadas principalmente em função das diferenças de abundância. As maiores abundâncias foram encontradas nas campanhas de verão (períodos chuvosos), especialmente em 2012, quando a densidade média de organismos atingiu 16.378 ind.m-3. As comunidades de inverno (períodos secos) apresentaram densidades relativamente baixas (médias de 4.054 em 2012 e 1.591 ind.m-3 em 2013). Contudo, variaram principalmente em termos diversidade, com os maiores valores observados para o Índice de Shannon. Durante os períodos de estudo foi registrado um total de 14 grupos taxonômicos no CEP, sendo a subclasse Copepoda a mais importante em termos de abundância e diversidade, representando 92% da abundância total com 22 espécies identificadas. As espécies mais abundantes e frequentes foram os copépodes Acartia lilljeborgi e Oithona hebes, seguidas por Pseudodiaptomus acutus e Temora turbinata, que apresentaram elevadas abundâncias e ocorrências mais pontuais. A composição zooplanctônica foi bastante homogênea durante campanhas amostrais, mas suas distribuições espaciais variaram de acordo com as condições hidrológicas predominantes em cada período. Os resultados indicaram fortes correlações entre a estrutura da comunidade e os parâmetros ambientais analisados, especialmente em função das variações climáticas sazonais. A distribuição das espécies foi possivelmente determinada por suas adaptações fisiológicas a condições específicas de salinidade. As variações de densidade, por outro lado, foram relacionadas à temperatura de água e as taxas de precipitação, particularmente responsáveis pelo incremento no fluxo de água doce e aporte de nutrientes no sistema durante períodos chuvosos. Palavras chave: Baía de Paranaguá; Zooplâncton; Copepoda; Estuário; Condições ambientais. / Abstract: Spatial and temporal dynamics of zooplankton assemblages were studied in the Paranaguá Estuarine System (Southern Brazil) including data from summer (rainy) and winter (dry) periods of 2012 and 2013. Organisms were collected with a cylindrical-conical net (200 ?m mesh) obliquely towed at 37 stations along the estuary. Environmental parameters were measured simultaneously. Variability in zooplankton abundance, composition and its relation to hydrological conditions were examined by multivariate techniques, as PCO and CAP. The results indicated significantly distinct assemblages, being abundance differences the major source of variability, predominantly over the temporal scale. Higher abundances were observed in summer communities, especially in 2012, when mean density reached 16378 ind.m-3. Winter assemblages, on the other hand, presented relatively lower densities but higher species diversity due to major intrusion of coastal waters. A total of 14 taxonomic groups were registered, being Copepoda the most abundant and diverse (92% of total abundance and 22 species identified). The coastal copepods Acartia lilljeborgi (44%) and Oithona hebes (26%) were the most important species both on abundance and frequency, followed by Pseudodiaptomus acutus (estuarine species) and Temora turbinata (neritic species). The composition and dominance were basically homogenous during the study period, but its spatial distribution distinctly varied along the estuary. Results suggested strong influences of environmental parameters in the community structure, especially in response to seasonal climatic variations. It is suggested that the species spatial distribution was mainly determined by its preferences and tolerances to specific salinity conditions. On the other hand, its abundances were strongly related to higher water temperature and precipitations rates, which possibly increased the nutrient inputs and food supply in the system due to intense continental drainage. Keywords: zooplankton; community variability; environmental changes; Paranaguá bay.

Made available in DSpace on 2014-06-12T22:58:05Z (GMT). No. of bitstreams: 2 arquivo1414_1.pdf: 1450162 bytes, checksum: bc31e0348f2f58754600e2155464b194 (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2009 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / O presente estudo procura acrescentar informações importantes sobre a biologia do Copepoda Pseudodiaptomus acutus (DAHL, 1894), como estudo da taxa de sobrevivência durante ciclo de vida, quando alimentado com diferentes espécies de microalgas oferecidas isoladamente e suas misturas. As coletas de plâncton foram realizadas na Ilha de Itamaracá (PE), ao longo da praia de Forno da Cal. As espécies de microalgas utilizadas durante os experimentos foram: Nannochloropsis sp. (Droop), Tetraselmis chuii (Butcher), Chaetoceros muelleri (Lemmermann) e Thalassiosira weissflogi (Grunow). Estas microalgas foram oferecidas aos diferentes estádios de vida do Copepoda hipoplanctônico P. acutus. Os Copepoda foram coletados em três arrastos, com rede de plâncton com 2 metros de comprimento, abertura de malha de 200 μm, 60 cm de diâmetro de boca e no final da rede um copo coletor de vidro. As amostras foram acondicionadas em recipiente de vidro com 2 litros de água do mar, em seguida as amostras foram acondicionadas em caixa térmica. As microalgas eram mantidas em meio F2 de Guillard, e os cultivos em meio F2 e F2 diluído (F2/2). P. acutus foi identificada, selecionada e cultivada em 10 placas de petri de 10 mL para cada tratamento, alimentados com uma espécie de microalga, e suas misturas com duas, três, quatro espécies de microalgas e sem alimento. Para verificar diferença significativa entre os tratamentos foram realizadas análise não- paramétrica Mann-whitney e Kruskal-Wallis. As duas espécies que apresentaram os melhores resultados foram às diatomáceas C. muelleri (cultivada em F2 e em F2/2), seguido por T. weissflogii (somente com F2). A mistura que apresentou o melhor foi com três espécies de microalgas cultivadas com meio F2/2. O pior foi encontrado com a Nannochloropsis sp. (tanto com F2 como com F2/2). Verificou-se que diferentes espécies de microalgas e diferentes misturas de microalgas influenciam diretamente no ciclo de vida, na mudança de estágio larval, e na sobrevivência. Estes resultados podem inserir a espécie P. acutus como alimento de outras espécies, devido ao estágio de náuplio permanecer ativo na coluna d água todo o tempo, seu pequeno tamanho e com movimentação constante, além das fêmeas produzirem uma média de 19 ovos e 15 náuplios. Sem falar que os náuplios e copepoditos possuírem taxas de sobrevivência superiores a 20%, mostrando-se relevantes para a maricultura

Submitted by Amanda Silva (amanda.osilva2@ufpe.br) on 2015-03-05T13:42:58Z No. of bitstreams: 2 TESE Melo, 2013. Efeito da turbulência sobre a migração vertical dos Copepoda no ASPSP.pdf: 1708035 bytes, checksum: 35601fcab60bb54c932b420aac911b4f (MD5) license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) / Made available in DSpace on 2015-03-05T13:42:58Z (GMT). No. of bitstreams: 2 TESE Melo, 2013. Efeito da turbulência sobre a migração vertical dos Copepoda no ASPSP.pdf: 1708035 bytes, checksum: 35601fcab60bb54c932b420aac911b4f (MD5) license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Previous issue date: 2013 / CNPq; SECIRM / A presente tese é composta de quatro manuscritos. Destes, dois foram desenvolvidos com o intuito principal de testar a hipótese de que “A turbulência é o principal agente estruturador da distribuição vertical dos Copepoda no Arquipélago de São Pedro e São Paulo (ASPSP), região tropical Equatorial do Atlântico, uma vez que ocorre uma intensificação dos processos turbulentos devido a sua topografia”. A partir do material analisado para testá-la, foram gerados dois manuscritos adicionais, um descrevendo uma anomalia morfológica em um indivíduo de Clausocalanus mastigophorus (Claus, 1863) e outro registrando a espécie Mormonilla phasma Giesbrecht, 1891 pela primeira vez em águas do Sudoeste do Atlântico. Para isto, foram realizadas coletas diurnas e noturnas em três campanhas (C1: junho/2010, C2: setembro/2011 e C3: outubro/2011), em duas estações fixas, uma a leste (S1) e outra a oeste (S2) do ASPSP. Amostras de plâncton foram coletadas da superfície aos 100 m de profundidade, considerando cinco camadas pré-determinadas de 20 m (L1: 0-20 m, L2: 20-40 m, L3: 40-60 m, L4: 60-80 m e L5: 80-100 m), através de arrastos verticais com rede de fechamento tipo Nansen (com área de boca de 0,28 m2 e malha de 200 μm). Para a caracterização termodinâmica do ambiente durante o período de realização das coletas, simultaneamente, foram obtidos perfis de CTD da superfície até 100 m de profundidade. Adicionalmente, foram realizados perfis verticais para a caracterização turbulenta do ambiente utilizando uma sonda perfiladora SCAMP, através da qual é possível inferir sobre os níveis de dissipação turbulenta a partir do gradiente vertical de temperatura (dT/dz). A SCAMP também é equipada com sensor de clorofila-a, o qual foi calibrado com amostras de água coletadas na superfície. Os resultados destacam a elevada biodiversidade da área, sendo observada a presença de 107 espécies, dentre as quais 57 não haviam sido registradas no ASPSP, em especial Mormonilla phasma, a qual teve seu primeiro registro no Atlântico Sudoeste. Não foram observadas diferenças significativas na comunidade quando comparados os períodos diurno e noturno, entretanto diferenças significativas foram observadas quando comparados os estratos superfície e subsuperfície. Os resultados observados indicam uma forte estabilidade vertical da comunidade de Copepoda no ASPSP, destacando a importância marcante da termoclina sobre a comunidade local, a qual delimita duas comunidades, uma acima e outra abaixo da mesma. Observa-se ainda uma grande variabilidade temporal a longo (C1 ≠ C2 e C3) e curto prazo (C2 ≠ C3). A turbulência apresentou variabilidade de até xiv três ordens de grandeza entre os perfis, variando entre 10-2 e 10-4. Os valores mais elevados foram observados na estação S1 e foi observada uma forte relação com a profundidade em ambas as estações, com os valores mais elevados nas camadas L1 e L2, e uma redução com o aumento da profundidade. Mesmo sendo considerado como uma área de amplificação de processos turbulentos, devido ao seu relevo, a elevada estratificação térmica e os níveis de clorofila-a são os principais agentes ambientais atuando diretamente sobre a distribuição dos Copepoda mesozooplanctônicos, enquanto que a turbulência atua sobre a comunidade de maneira indireta.

Aspects of the biology of the calanoid copepod Pseudodiaptomus hessei are described, with particular reference to its vertical migratory behaviour. The present investigations were carried out largely by means of Nansen-type plankton nets, but several new pieces of apparatus were developed and. are described herein. The daytime vertical distribution of P. hessei varies according to developmental stage and depth of water. In shallow areas of the lake the entire population is benthic or in very close association with the lake bed. In the deepest part of the lake (40m) the naupliar and early (i.e. C I - C III) copepodite stages are essentially pelagic, but the adult and late (i.e. C IV - C V) copepodite stages are predominantly benthic and may be quiescent or infaunal. During the hours of darkness, the calanoids are distributed through the water column. The nauplii are consistently abundant in the surface waters but the distribution of the other stages is not regular. The distribution can be related to lunar intensity in many cases, with the post-naupliar stages frequently occurring deeper in the water column on bright moonlight nights and in the surface waters on overcast moolnless nights. The dusk ascent and dawn descent of the calenoids is clearly related to changes in light penetration in most individuals. The movements of a fraction of the adults occur in the apparent absence of adequate light cues. This behaviour is shown more extensively by the adult females. An endogenous activity rhythm has been shown in the species under laboratory conditions and it is suggested that this may play a part in the migratory movements. A basic examination of the feeding methods, feeding appendages and food sources of adult and late copepodite stages has been made. Changes in feeding intensity through twenty-four have been examined in the field and under laboratory conditions. Using as an index of feeding intensity, the proportion of animals with food in their guts, it has been shown that a pronounced diel difference occurs in adult calanoids in the lake. Feeding is almost entirely restricted to the nocturnal presence of the calanoids in the water coloumn. This difference exists in the pre-adult copepodite stages, but is not nearly as striking. The absence of feeding during daylight is not readily accounted for in terms of food availability and it is attributed to the quiescent or possible infaunal existence of the adults. A periodicity in egg hatching has been shown Naupliar release from the parental egg sac is predominantly a nocturnal phenomenon in the hot and cool seasons. It is suggested that this may be important in attaining a favourable vertical distritution for the nauplii, and may be important in the distribution of the species. A preliminary acccunt of the seasonal cycle and population dynamics of P. hessei is given, based on data collected over two years at a single station. Seasonal changes in calanoid abundance are intermediate between those recorded in truly tropical areas and in temperate latitudes. Potential food sources show relatively little change. The vertical migration of P. hessei is considered in relation to its apparent ecological significance and comparisons are drawn with observations made on the same species or other pseudodiaptomids in estuaries and lagoons elsewhere.

Mesozooplankton community structure and grazing impact in the Polar Frontal Zone (PFZ) of the Southern Ocean were investigated during two cruises of the South African National Antarctic Programme (SANAP), the Marion Offshore Ecosystem Variability Study I & II (MOEVS). During the first cruise (MOEVS I), a meso-scale oceanographic grid survey was conducted in the upstream region of the Prince Edward Islands (PEI) in austral autumn (April) 2001. Mesozooplankton samples, collected using a Bongo net (fitted with 200 and 300µm mesh nets) at depths between 200 and 300 m, were separated into three size fractions: 200-500 µm; 500-1000 µm; 1000-2000 µm by reverse filtration. Total surface (depth <5 m) chlorophyll-a (chl-a) concentration (measured fluorometrically) during the study ranged between 0.11 and 0.34 µg 1^(-1) and was always dominated by picophytoplankton (<2.0 µm). Total mesozooplankton abundance and biomass during the survey ranged between 49 and 1512 ind. m^(-3) and between 0.7 and 25 mg Dwt. m^(-3), respectively. Throughout the survey, the 200-500 µm class numerically dominated the mesozooplankton community, comprising an average of ~ 69% (SD = ± 12.3%). The dominant species in the 200-500 µm size fraction were the copepods Oithona similis, Calanus simillimus and Metridia lucens and the pteropod, Limacina retroversa. However, in terms of biomass, the 1000-2000 µm group was predominant, with dry weight values constituting an average of ~ 66% (SD = ± 10.2%). Biomass was dominated by carnivorous zooplankton, particularly the euphausiids, Euphausia vallentini and Thysanoessa vicina and the chaetognaths, Sagitta gazellae and Eukrohnia hamata. Three distinct groupings of stations were identified by multivariate analysis. The different station groupings identified reflect changes in the relative contributions of the rather than different species assemblages. During the second cruise (MOEVS II), conducted in April 2002 (austral autumn), mesozooplankton community structure and grazing impact were investigated at 13 stations in the west Indian sector of the PFZ. Total integrated chl-a biomass ranged between 11.17 and 28.34 mg chl-a m^(-2) and was always dominated by nano- and picophytoplankton (<20 µm). Throughout the study, small copepods, mainly Oithona similis and Ctenocalanus vanus, numerically dominated the mesozooplankton community comprising up to 85% (range 30 to 85%) of the total abundance. Grazing activity of the four most abundant copepods (O. similis, C. vanus, Calanus simillimus and Clausocalanus spp.), which comprised up to 93% of total mesozooplankton abundance, was investigated using the gut fluorescent technique. Results of gut fluorescence analyses indicated that C. simillimus, Clausocalanus spp. and Ctenocalanus vanus exhibited diel variability in gut pigments, with maximum values at various stages of the night. In contrast, O. similis did not demonstrate diel variation in gut pigment contents. Ingestion rates of the four copepods ranged from 23.23 to 1462.02 ng (pigm.) ind^(-1) day^(-1), depending on the species. The combined grazing impact of the four copepods, ranged between 1 and 36% of the phytoplankton standing stock per day, with the highest daily impact (~ 35.86%) occurring at stations in the vicinity of the Antarctic Polar Front. Among the copepods, O. similis and C. vanus were generally the most important consumers of phytoplankton biomass; together they were responsible for up to 89% (range 15 to 89%) of the total daily grazing impact. Carbon specific ingestion rates of the copepods varied between 42 and 320% body carbon per day, depending on the species. The study highlights the importance of small copepods in terms of both their significant contribution to total mesozooplankton numbers and their grazing impact on the phytoplankton standing stocks in the PFZ during austral autumn.

The aim of the present study was to assess the ecological role of the euthecosome pteropod, Limacina retroversa, in particular, and the mesozooplankton community, in general, in the pelagic ecosystem of the Polar Frontal Zone (PFZ), Southern Ocean. Data were collected from four oceanographic surveys to the Indian sector of the PFZ during austral autumn 2000, 2002, 2004 and 2005. Copepods, mainly Calanus simillimus, Oithona similis, Clausocalanus spp. and Ctenocalanus spp., typically dominated total mesozooplankton counts, accounting for, on average, between 75.5 % and 88.1 % (Mean = 77.4 %; SD = 13.4 %) of the total, during the present investigation. Results of the study indicate that L. retroversa may, at times, contribute substantially to total mesozooplankton abundances. During the study, L. retroversa contributed between 0.0 and 30.0 % (Mean = 5.3 %; SD = 7.1 %) to total mesozooplankton numbers. Significant small-scale variability in abundance and size structure of L. retroversa and abundance of copepods was minimal. Inter-annual variability, on the other hand, was significant between some years. Total pteropod numbers were greatest during April 2002 and 2004, while copepods exhibited greatest abundances during April 2004 only. Pearson’s Correlation analysis suggested that L. retroversa abundances were positively correlated to total surface chlorophyll-a (chl-a) concentrations. The significantly lower chl-a concentrations recorded during April 2005 may explain the reduced pteropod numbers observed during that survey. The size class structure of L. retroversa comprised mainly small and mediumsized individuals during all four surveys. This corresponds well with records from the northern hemisphere (sub-Arctic and Arctic waters) where Limacina spp. are reported to exhibit maximum spawning during mid to late-summer. Higher abundances of large individuals only occurred during April 2005, when chl-a concentrations were very low; possibly the result of delayed spawning, due to reduced food availability. Ingestion rates of the four most abundant copepods, determined using the gut fluorescence technique, ranged between 159.32 ng (pigm) ind⁻¹ day⁻¹ and 728.36 ng (pigm) ind⁻¹ day⁻¹ (Mean = 321.01 ng (pigm) ind⁻¹ day⁻¹; SD = 173.91 ng (pigm) ind⁻¹ day). Ingestion rates of L. retroversa were much higher, ranging from an average of 4 28.68 ng (pigm) ind⁻¹ day⁻¹ in April 2002 to 4 196.88 ng (pigm) ind⁻¹day⁻¹in April 2005 (Mean = 4157.36 ng (pigm) ind⁻¹ day⁻¹; SD = 35.37 ng (pigm) ind⁻¹day⁻¹). Average daily grazing rates for the pteropod varied between 0.39 mg (pigm) m⁻² day⁻¹ in April 2005 and 17.69 mg (pigm) m-2 day-1 in April 2004 (Mean = 6.13 mg (pigm) m⁻² day⁻¹; SD = 11.04 mg (pigm) m⁻² day⁻¹); corresponding average daily grazing impacts ranged between 8.4 % and 139.8 % of the phytoplankton standing stock in April 2005 and 2004, respectively (Mean = 48.5 %; SD = 84.5 %). Average daily grazing rates of the four copepods ranged from 4.58 mg (pigm) m⁻² day⁻¹ to 8.77 mg (pigm) m⁻² day⁻¹ -1, during April 2002 and 2004, respectively (Mean = 6.28 mg (pigm) m⁻² day⁻¹; SD = 5.94 mg (pigm) m⁻² day⁻¹). Collectively, the copepods removed an average of between 31.6 % and 89.8 % of the phytoplankton standing stock per day, during April 2002 and 2004, respectively (Mean = 70.8 %; SD = 86.7 %). The daily grazing impact of the copepods accounted for an average of between 40.4 % and 87.8 % of the total zooplankton grazing impact, during April 2004 and 2005, respectively (Mean = 75.0 %; SD = 65.5 %). L. retroversa was responsible for an average of 52.4 % and 59.5 % of the total zooplankton grazing impact, during April 2002 and 2004, respectively. However, during April 2005, when L. retroversa numbers were significantly lower than previous years, the pteropod contributed an average of only 7.5 % to the total zooplankton grazing impact. Thus, during the present investigation,the pteropod was responsible for removing a mean of 48.9 % of the available phytoplankton (SD = 74.9 %). The predation impact of the dominant carnivorous macrozooplankton and micronekton in the PFZ was determined during April 2004 and 2005 using daily ration estimates obtained from the literature. Additionally, gut content analysis was used to determine the contribution of L. retroversa to the diet of the dominant predators. Average predation impact ranged from 1.1 % and 5.7 % of the total mesozooplankton standing stock during April 2004 and 2005, respectively (Mean = 3.8 %; SD = 12.3 %). Chaetognaths and euphausiids dominated total carnivore numbers and made the greatest contributions to total predation impact during both years. Copepods appeared to be the main prey item of the dominant carnivorous macrozooplankton-micronekton in the region. L. retroversa was only detected in the gut contents of the amphipod, Themisto gaudichaudi, but not in either of the chaetognath species (Eukrohnia hamata and Sagitta gazellae) or the myctophid fish (Electrona spp.). The pteropod was found in 19 % of amphipod guts dissected. Pearson’s Correlation analyses showed that the four major predatory zooplankton groups found in the PFZ (chaetognaths, euphausiids, amphipods and myctophid fish) were positively correlated to abundances of L. retroversa, suggesting that the pteropod might be an important prey item for many of the carnivorous macrozooplankton/micronekton in the PFZ. To conclude, L. retroversa may play an important role in the pelagic ecosystem of the PFZ, in austral autumn. However, ocean acidification and calcium carbonate undersaturation (as a result of increased anthropogenic carbon dioxide emissions), that is predicted to occur within the next 50 – 100 years, will most likely have significant implications for the Sub-Antarctic pelagic ecosystem if L. retroversa cannot adapt quickly enough to the changes.

The standing crop of the copepod G. b. thomasi Forbes in Marion Lake, B. C, has been recorded during 1966 and 1967. These copepods excysted as stage IV copepodids during April and moulted to adults, which produced eggs in May. The new population developed to the copepodid IV stage by mid-summer, when 85 % of the animals returned to the bottom and encysted. The copepodids of stage IV and V and the adults are predators. In the laboratory, six groups of animals were presented separately to the predator, which preyed most efficiently on cyclopoid nauplii and copepodids, diaptomid nauplii and rotifers; and least efficiently on diaptomid copepodids and cladocera. In the lake, the forms least affected by cyclopoid predation were also the diaptomid copepodids and cladocera. There was a correlation between C. b. thomasi encystment and food shortage, which suggests that food shortage may stimulate encystment of stage IV copepodids. / Science, Faculty of / Zoology, Department of / Graduate

During some years Neocalanus plumchrus overwinters in Saanich Inlet while in other years they are absent from the fjord (Harrison et al., 1983). The cause of this variation is not known but the annual development of anoxic conditions followed by an intrusion of dense, oxygenated water, was suspected to influence their distribution and abundance. Vertical and horizontal haul samples collected from Saanich Inlet indicated the overwintering population in 1985 (September 1985 to March 1986) was sparse; in September 1986 the population of N. plumchrus was comparably low. In the spring and summer, N. plumchrus is introduced from the Strait of Georgia and Juan de Fuca Strait, and in some years may arise from reproduction within the inlet. So few adults were collected at the three stations in Saanich Inlet in January-March 1986 (<0.20 m⁻³) that their potential contribution to the spring population was considered negligible. Decline in the overwintering population in September 1985 and 1986 appears to be correlated with the occurrence of an extensive deep water renewal. The distribution of N. plumchrus during early stages of their deep water migration (June to August), is influenced by the low oxygen concentrations in the bottom of the inlet (i.e. 0.10-0.30 mL L⁻¹). During the renewal, copepods occurred above the oxygen minimum (75 m) possibly due to their displacement or their avoidance of the low oxygen zone. Subsequently, they were exposed to tidal transport out of the inlet and perhaps to increased predation. On two occasions in which N. plumchrus was present during the winter in Saanich Inlet (1969 & 1974), a high volume of dense water intruded, disrupting the copepod layer during the mixing of the two water masses. Even though a greater volume of water left the inlet some of the copepods could have remained in the water, below sill depth. Neocalanus plumchrus successfully overwinters and reproduces in Sechelt Inlet which is well-oxygenated but has a very shallow sill (15 m) that 'locks' the copepods into the inlet. The fifth copepodite stages also occupy deeper depths in Sechelt Inlet than in Saanich Inlet, even though the bottom depths are comparable. In low oxygen tolerance experiments many factors such as the period of captivity, and the region of origin (i.e. Saanich Inlet versus the Strait of Georgia) caused variable results. Although the minimum oxygen level tolerable during their migration could not be determined, N. plumchrus tolerated levels as low as 0.56 mL L⁻¹ (12% mortality). Sediment trap samples indicate that a massive die off could not account for the loss of N. plumchrus from Saanich Inlet. / Science, Faculty of / Zoology, Department of / Graduate

The main purpose of this study is to describe the population ecology of eight species of harpacticoid copepods over a period of one year with emphasis on the effects of physical interactions and biotic factors on these populations. The species were: Amphiascopsis sintus (Claus) 1866, Stenhelia (D.) oblonga Lang, 1965, Heterolaphote variables Lang, 1965, Ectinosoma melaniceps Boek ? var. T. Scott, 1902, Paralophonte subterraneas Lang, 1965, Tisbe furcata (Baird) 1837, Diasaccus spinatus Cambell, 1929 and Parathelestris bulbiseta Cambell?.