Graduation date: 1980

This thesis presents the results of an investigation on the relationships between populations of closely related animals under apparent sympatric conditions. The mechanisms found have particular application toward understanding the species problem among members of the free-swimming marine copepod genus Calanus that possess a toothed inner surface on the coxopodites of the fifth pair of swirnming legs. The investigation describes the morphology, distribution, and general ecology of two forms of toothed Calanus from the far eastern North Pacific Ocean. Morphological differences were established and used to distinguish both forms on the oasis of length, shape of the anterior surface of the cephalothorax, proportionate differences in segments of the urosome and fifth swimming legs, and by the degree of asymmetry in the fifth pair of swimming legs of males. An additional feature was the length of a small spine on the fifth swimming legs of both forms. A general account of the distribution and ecology of both forms from Glacier Bay, Alaska, to the Mexican Border was derived from data gathered during several long cruises. The Large Form was found from Glacier Bay, Alaska, to Cape Mendocino, California. The Small Form was found from the Mexican Border to the vicinity of Vancouver Island, British Columbia. Along the outer coast, the Large Form appeared to be associated with Pacific Sub-Arctic water typical of the California Current, whereas the Small Form appeared to be associated with the warmer more saline water typical of Equatorial Pacific water associated with the Davidson Counter Current. A detailed analysis of the ecological relationships of both forms in a region of overlap was performed in Indian Arm, an inlet near Vancouver, British Columbia. In this inlet, the Large Form was generally associated with the cooler more saline deep water of the inlet. The Small Form occurred at shallower depths. Overlap between the populations of both forms was limited to Large Form females that rose to shallower depths during part of the year occupying nearly the same portion of the water column as the Small Form population. The yearly cycles of both forms in Indian Arm were shown to be different indicating different times of breeding for Large and Small Forms. On the basis of morphology and previous descriptions for toothed members of the genus Calanus, the Large Form appeared to be Calanus glacialis and the Small Form C. pacificus californi-cus. Based on the results of the distributional study and the ecological study, it was concluded that both forms were behaving as good species since separation of breeding populations both spatially and temporally appeared to be real, and the likelihood of interbreeding appeared to be small. In the classical sense, the two species are sympatric because their ranges overlap, and there is a strong indication that interbreeding occurs infrequently if at all. Association to different types of water and differences in yearly cycles appear to be the primary mechanisms that act to maintain the integrity of sympatric species. The vertical as well as horizontal space must be given equal consideration in planktonic studies. Under these conditions, therefore, the toothed Calanus spp. of Indian Arm are allopatric with respect to the water column. / Science, Faculty of / Zoology, Department of / Graduate

Thesis (Ph. D.)--University of Rhode Island, 2005. / Typescript. Includes bibliographical references (leaves 252-262).

The relationship between Calanus plumchrus and hydrographic parameters has been investigated. The copepod is associated with Strait of Georgia bottom water from July to January. This association is not found in the early developmental stages, which are present from February to July and are most commonly in near surface waters. The onset of maturation and breeding precedes the spring phytoplankton bloom; some environmental parameters appear to function as cues to this timing. The nature of these cues is not clear; no single parameter would seem to be capable of producing the observed effect. C. plumchrus overwinters in a state of arrested development similar to diapause. / Science, Faculty of / Zoology, Department of / Graduate

Thesis (M.S.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 61-67). Also available on the World Wide Web.

L’hybridation est un phénomène observé tant chez les plantes que chez les animaux, mais qui n’avait toutefois jamais été détecté chez le zooplancton marin. Cette thèse vise à caractériser l’hybridation entre Calanus glacialis et C. finmarchicus afin d’évaluer son impact sur la dynamique des populations dans l’ouest de l’Atlantique. De plus, les méthodes d’identification morphologique et génétique sont comparées et combinées afin de tester leur capacité à discriminer les espèces parentales et les hybrides. Dans le deuxième chapitre, une grande variabilité spatio-temporelle du chevauchement de la longueur de prosome entre les espèces C. glacialis et C. finmarchicus est montrée pour les copépodites de stade V. Ce chevauchement de taille entraine une identification erronée et donc, une sous-estimation considérable de l’abondance de C. glacialis dans l’estuaire du Saint-Laurent et sur la côte du Labrador. Au troisième chapitre, la présence d’hybrides est d’abord établie. Il existe une grande variabilité spatiale dans la fréquence des hybrides dans la zone hybride, soit de l’archipel canadien arctique au golfe du Maine, chez le stade copépodite V. De plus, la longueur de prosome des hybrides varie en fonction des génotypes dans l’aire d’étude. Dans le quatrième chapitre, il est mis en évidence que la phénologie reproductive des femelles adultes hybrides est intermédiaire à celles des espèces parentales dans l’estuaire du Saint-Laurent. En revanche, le succès reproducteur et le phénotype des femelles adultes hybrides sont similaires à ceux de leur ancêtre maternel. Les hybrides représentent une faible proportion de la production totale d’œufs de mars à juillet. Ainsi, malgré la présence de flux génique entre C. glacialis et C. finmarchicus, les espèces parentales conservent leur intégrité et sont isolées temporellement dans la zone hybride. Les effets sur la dynamique des populations des espèces parentales semblent minimes. Les recherches à vernir devraient tenter de révéler l’hybridation entre ces espèces dans d’autres zones et d’investiguer l’effet des variations de phénologie reproductive et d’advection sur l’abondance d’hybrides. L’hybridation entre d’autres espèces de zooplancton marin semble également plausible. / Hybridization is a phenomenon observed in plants and animals which to date has never been detected in marine zooplankton. This thesis aims to characterise hybridization between Calanus glacialis and C. finmarchicus in order to evaluate the impact on species population dynamics in the West Atlantic. In addition, morphological and genetic identification were compared and combined to test their potential for discrimination of parental species and hybrids. In the second chapter, a great spatio-temporal variability in overlap in prosome length between C. glacialis and C. finmarchicus is shown for stage V copepodites. This overlap in prosome length has the consequence of misidentifying and thus, considerably underestimating C. glacialis’ abundance in the St. Lawrence Estuary and on the Labrador Coast. In the third chapter, it is shown that hybrids exist, and that there is substantial spatial variability in their frequency in the hybrid zone, from the Canadian Arctic Archipelago to the Gulf of Maine, for the copepodite stage V. Moreover, hybrid size varied as a function of genotypic composition. In the fourth chapter is shown that hybrid adult females have an intermediate reproductive phenology to that of their parental species in the St. Lawrence Estuary. Contrastingly, fitness and phenotypes of hybrid adult females are similar to those of their maternal ancestor. Hybrids represent a small proportion of total egg production from March to July. Thus, although gene flow occurs between these species, parental species are maintained and mainly isolated temporally within the hybrid zone. The effects of hybridization on species population dynamics are probably minor. Future studies should aim to study hybridization between these species in other zones and the effects of variation in their reproductive phenology and advection on hybrid abundance. Hybridization between other marine zooplankton species is also likely.

Calanus helgolandicus is a key copepod species occurring in the North East Atlantic that is responding to oceanic warming through an expansion of its geographic range. This range extension has led to concerns about how this may affect ecosystem trophodynamics. Here I investigate the interannual variability and seasonality of C. helgolandicus, using a ~28 year time-series from the western English Channel (station L4). I focus specifically on the role of mortality, as a key life history process that is challenging to quantify and historically has received little attention. C. helgolandicus abundance remained within a narrow ~four-fold interannual envelope, which was a consequence of multiple losses that removed ~99% of the potential population. Loss of early life stages occurred through the incidence of non-viable eggs and abnormal nauplii (both higher in spring), and via predation; egg mortality rates were positively correlated with C. helgolandicus copepodite abundance and total copepod biomass, indicative of intraguild predation and cannibalism. By contrast, late-stage copepodite mortality rates were highest in autumn, and were positively related to gelatinous predator abundance and biomass (medusae, ctenophores and chaetognaths). Molecular gut-content analyses revealed that two abundant jellyfish species present during 2015 (Pleurobrachia pileus and Leuckartiara octona) both preyed on C. helgolandicus. Adult male consumptive mortality rates were ~6 times higher than that of adult females; whereas male non-consumptive rates were only ~1.5 times that of females, providing evidence that predation was the primary mortality source in males. Non-consumptive mortality rates contributed 0-54% (median of 4.5%) to total mortality and were positively related to the 72-hour maximum wind speed, implying that turbulence created during extreme weather events may increase zooplankton mortality. I conclude that C. helgolandicus population control is modulated via a series of mortality-related losses occurring through the different development stages; from reduced egg viability to predation of copepodites by gelatinous carnivores. Although I find little evidence for changing ecosystem trophodynamics at L4, my results contribute to the knowledge of C. helgolandicus population dynamics at a site near the centre of its distribution, and suggest that a future expanding population may be a valuable food source for a variety of predators.

Thesis (M.Sc.)--Memorial University of Newfoundland, 2002. / Bibliography: leaves 193-200.

Zooplankton are the major primary consumers in pelagic ecosystems, providing the principal pathway for energy transfer from primary production to higher trophic levels. The marine copepod Calanus finmarchicus is an important component of the pelagic food web in the North Atlantic and peripheral ecosystems, and forms an essential dietary component of a number of commercially important fish. As part of its life cycle, many C. finmarchicus overwinter in a diapause phase (a dormant overwintering phase where development is suppressed in adaptation to the seasonal food supply) at depths of 500 to 2000 m, but little is known about the triggers that initiate and terminate diapause, or the internal processes associated with these triggers. Understanding these processes is important, given that subtle changes in the environmental conditions which may affect diapause could have consequences for the entire Calanus-based ecosystem. In this study I took advantage of relatively easy access to a deep (> 100 m), isolated population of C. finmarchicus in Loch Etive (a sea loch on the west coast of Scotland) to sample Calanus finmarchicus monthly between April 2006 and June 2007 and measure lipid dynamics and gene expression associated with diapause. Chapter 1 of this thesis provides a general introduction to diapause and Calanus finmarchicus, Chapter 2 reports on the population of C. finmarchicus in Loch Etive, Chapter 3 reports changes in the lipid class and fatty acid composition of individual copepods, Chapter 4 reports on differential gene expression between diapausing and active C. finmarchicus and Chapter 5 provides a general discussion and puts this research into context. This study provides some initial insight into possible gene expression patterns, but further work is needed to attribute specific gene expression patterns with initiation and termination of diapause.

Thèse ou mémoire avec insertion d'articles / Les copépodes dominent la biomasse du mésozooplancton des régions arctiques et subarctiques, où lumière, glace et production primaire varient fortement selon les saisons. En transformant le carbone fixé par les microalgues en réserves lipidiques pour survivre l'hiver, les Calanus spp. constituent une source d'énergie cruciale pour les poissons, oiseaux et mammifères marins. Historiquement, les copépodes sont étudiés par un comptage taxonomique après un échantillonnage par filets. Cette thèse propose un autre paradigme en combinant l'utilisation d'outils d'imagerie plus récents et une approche dite « par traits fonctionnels ». Les traits fonctionnels sont des propriétés mesurables à l'échelle individuelle et influençant le succès écologique des organismes (i.e. taille, régime trophique, migration verticale). Ils sont partagés par plusieurs espèces et peuvent être reliés à des fonctionnalités des écosystèmes comme l'export de carbone ou l'énergie disponible pour les réseaux trophiques par exemple. Comme une majorité des traits possèdent une signature morphologique, nous les avons définis sur deux types d'images individuelles du plancton, complémentaires et couramment utilisées : des images in situ de l'Underwater Vision Profiler (UVP) et des images en couleur prises lors d'observations au stéréomicroscope. L'objectif de cette thèse est de comprendre comment les traits fonctionnels des copépodes, identifiés sur des images, peuvent être reliés aux dynamiques environnementales et au fonctionnement des écosystèmes arctiques et subarctiques. Dans le Chapitre 1, nous analysons des images in situ prises par l'UVP au moment de la fonte printanière de la banquise dans l'arctique canadien. Des variables morphologiques sont utilisées pour projeter les images dans un espace statistique, et les axes synthétisent les variations morphologiques en trois traits continus : la taille, l'opacité (qui nous renseigne sur les structures pigmentées), et la complexité du contour (indiquant probablement un taux d'activité par la visibilité des appendices). Cette analyse exploratoire a révélé des traits nouveaux, dont les variations étaient fortement corrélées à la fonte de la banquise et à l'efflorescence des algues. Plusieurs arguments indiquent que les maxima d'opacité des individus peuvent être attribués à la présence d'astaxanthine, un pigment caroténoïde rouge. Dans le Chapitre 2, une revue de la littérature a mis en évidence les conditions écologiques propices à la coloration des copépodes pour divers écosystèmes aquatiques à l'échelle globale. Nous démontrons que la pigmentation rouge peut participer au succès des individus (croissance, survie, reproduction) grâce aux propriétés antioxydantes de l'astaxanthine. Comme la pigmentation semble ajustable à de courtes échelles temporelles et avantageuse dans diverses conditions environnementales (lumière intense, basses températures et couvert de glace, ou grandes profondeurs), nous pensons qu'elle peut être considéré comme un de "couteau-suisse" de protection métabolique. Dans le Chapitre 3, une méthode de déconvolution de la couleur de l'astaxanthine a été utilisée pour produire un indice de rougeur sur des images de copépodes arctiques observés au stéréomicroscope. L'indice a été validé par comparaison avec une quantification chimique des pigments, et peut être utilisé pour des images prises dans diverses conditions grâce à une étape préalable de calibration des canaux de couleur. Cette thèse montre qu'il est possible d'extraire un maximum d'information à partir d'une image de plancton pour dégager des tendances écologiques sur de grands jeux de données, tout en gardant accès à la variabilité interindividuelle. Utiliser les traits définis ici (taille, pression de broutage, taux d'antioxydants), en combinaison avec d'autres outils, pourrait participer à la compréhension du fonctionnement des réseaux trophiques. / Copepods dominate the mesozooplankton biomass of arctic and sub-arctic regions, where light, ice and primary production are highly variable according to the season. By converting carbon fixed by microalgae into lipid reserves for winter survival, Calanus spp. are a crucial source of energy for fish, birds and marine mammals. Historically, copepods have been studied by taxonomic counting after net sampling. This thesis proposes an alternative paradigm by combining the use of more recent imaging tools and functional trait-based approach. Functional traits are properties that are measurable at the individual scale and influence the ecological success of organisms (i.e. size, trophic regime, vertical migration). They are shared by several species and can be related to ecosystem functionalities such as carbon export or energy available for food webs for example. As a majority of them have a morphological signature, we defined them on two types of individual plankton images, complementary and commonly used: in situ images from the Underwater Vision Profiler (UVP) and color images taken during stereomicroscope observations. The objective of this thesis is to understand how functional traits of copepods, identified in images, can be related to environmental dynamics and functioning of arctic and sub-arctic ecosystems. In Chapter 1, we analyze in situ images taken by the UVP at the time of spring melt in the Canadian arctic. Morphological variables are used to project the images into a statistical space, and the axes synthesize morphological variation into three continuous features: size, opacity (which tells us about pigmented structures), and complexity of contour (likely indicating feeding activity through appendage visibility). This exploratory analysis revealed novel traits, having variations strongly correlated with sea ice melt and algal blooms phenology. Several arguments indicate that opacity maxima in individuals can be attributed to the presence of astaxanthin, a red carotenoid pigment. In Chapter 2, a review of the literature highlighted the ecological conditions conducive to copepod coloration for various aquatic ecosystems on a global scale. We demonstrate that red pigmentation can participate in the success of individuals (growth, survival, reproduction) through the antioxidant properties of astaxanthin. Since pigmentation appears to be adjustable on short time scales and advantageous under various environmental conditions (intense light, low temperatures and ice cover, or great depths), we believe it can be considered as a "swiss army knife" of metabolic protection. In Chapter 3, an astaxanthin color deconvolution method was used to produce a redness index on stereomicroscope images of arctic copepods. The index was validated by comparison with a chemical quantification of the pigments, and can be used for images taken under various conditions thanks to a prior calibration step of the color channels. This thesis shows that it is possible to extract a maximum amount of information from a plankton image to identify ecological trends on large datasets, while keeping access to inter-individual variability. Using the traits defined here (size, grazing pressure, antioxidant levels), in combination with other tools, could participate in understanding the functioning of food webs.