Faculty Projects and Publications

Delphine Thibault-Botha

Assistant Researcher

Office: (808) 236-7457
Fax: (808) 236-7443
Email: dthibaul@hawaii.edu
Hawai‘i Institute of Marine Biology
PO Box 1346
Kane‘ohe, HI 96744

Education

Ph.D. 1994, Oceanography, University of Aix-Marseilles II, Oceanology Center of Marseilles. Zooplankton nutrition and metabolism in frontal areas of the Mediterranean Sea (Almeria-Oran front, Rhone River plume).
M.S. 1990, Oceanography (French DEA), University of Aix-Marseilles II. Remote sensing study of oceanic structures of the tropical Atlantic Ocean, study case of the equatorial upwelling.
1989, Maîtrise d’Océanographie Biologique, Université de Bretagne Occidentale (Brest). Major: Biological Oceanography.
1988, Licence de Biologie des Organismes, Université de Bretagne Occidentale (Brest). Major: Biology.
1987, Diplômes d’Etudes Universitaires Générales section biologie, Université de Nantes. Major: Biology.

Research Interests

My primary research interests lie in the understanding of the copepods community structure and metabolism and their linkage with regions showing strong physical forcing such as in frontal zones (geostrophic and salinity fronts) and peculiar environments such as the North East Pacific Ocean, HLNC area of the North Pacific Ocean and the Arctic and Antarctic Oceans.
A focal point in some research I have been conducted concern the clear importance of match/mismatch between zooplankton metabolism and changes in spatial and temporal scales, which is important in understanding population distribution. For example the higher nutrition activity observed in the frontal areas should dwell more energy towards the secondary production (egg production rates measurements). But this appeared only true in hydrological environment with low temporal and spatial variability. Each frontal area therefore appeared different in its impact on the zooplankton community with in some cases a good coupling (Alboran Sea) or a de-coupling between the phytoplankton and the zooplankton biomass. I have also been interested in understanding the impact of the zooplankton population on the regulation of the biogenic carbon, and other chemicals (i.e. pollutants).
I have, lately, been more and more interested in the impact of underestimated and understudied zooplanktonic taxa, such as gelatinous zooplankton and their predator-prey relationships. Carnivorous and omnivorous gelatinous zooplankton are not only food for fish (commercial and non-commercial species), but they are also predators on, and competitors with, larval fish. I have studied then a wide range of planktonic invertebrate species (ctenophores, siphonophores and medusae, chaetognaths, and salps) and learnt much about the biology and ecology of the different groups in different environments. The data collected during different studies (see below) have allow me to answer questions on zooplankton feeding, but also allowed me to get a fuller picture of zooplankton behavior and in turn community structure.
Copepods

Metabolism of species target (Copepods) in the North East Pacific Ocean: program GLOBEC-NEP
Our process studies focused on understanding zooplankton in situ population dynamics processes and the interaction between physical and biological processes. We used the gut fluorescence technique on different stages and sizes of target species (Calanus marshallae, Pseudocalanus sp.) as a direct index of feeding activity. Spatial variability of gut fluorescence reflects variability in nutritional state, and may be positively correlated with other proxies of high growth rate.
Collaborators: Mark Huntley (Univ. of Hawai‘i), Meng Zhou (Boston Univ.), Bill Peterson (Oregon State Univ.), Rob Campbell (Univ. of Victoria)
Arctic Ocean
The biomass, species and chemical composition of the mesozooplankton and their impact on lower food levels have been estimated along a transect across the Arctic Ocean during AOS’94. Primary production, mesozooplankton biomass and biomass of other components of this ecosystem were higher than previously reported. According to measurements of gut pigment and gut turnover rates, the mesozooplankton on average ingested between 6 and 30% of their body carbon per day as phytoplankton. Microzooplankton may have provided an additional source of energy for the mesozooplankton community. These data emphasize the importance of mesozooplankton in the arctic food web and reinforce the idea that the Arctic Ocean should no longer be considered to be a “biological desert.” New data collected over the Canada Basin in summer 2002 as well as data from programs SHEBA and SBI will be combined to see if changes in the mesozooplankton population in this part of the Arctic Ocean occurred over the past 10 years.
Collaborators: Erica Head (Bedford Inst. of Oceanography), Russ Hopcroft (Univ. of Alaska Fairbanks)

Gelatinous zooplankton

Importance of gelatinous zooplankton (ctenophore and siphonophores) population in the North East Pacific Ocean in summer.
In summer 2002, during the GLOBEC mesoscale cruise #4 in the North East Pacific Ocean an unusually low number of copepods was collected. Potential contribution of gelatinous zooplankton to this reduction in density was evaluated. Ctenophores and siphonophores were present in large numbers and their potential feeding rates were measured through different techniques (gut fullness, feeding experiments). New insight of the deleterious role of gelatinous zooplankton in the North East Pacific Ocean will be quantified. Impact of formalin preservation on ctenophores has been re-evaluated and new values obtained. Published values of predation impact based on preserved sampled should be revisited.
Siphonophores population in the Agulhas Current (East coast of South Africa),
Spatio-temporal patterns in the composition and structure of siphonophore assemblages along the east coast of South Africa were studied from samples collected during the austral autumn, spring and summer of 1990-1991, and examined in relation to the large-scale hydrography of the region. This study is the first to report detailed taxonomy of the siphonophores population on the East coast of South Africa. The Agulhas Current has been lacking serious biological studies and so far only of few articles has been published, whilst its physical characteristics has been well established. Three relatively distinct provinces could be discerned that corresponded to the Agulhas Current proper, to the shelf inside the current and to an upwelling cell in the extreme south. Patterns of species diversity and zoogeography generally conformed to the large-scale hydrography, and highest numbers of species were observed in samples collected from within the Agulhas Current. Lowest diversity was recorded from waters in the current-driven upwelling cell to the south, where assemblages were characterised by dense populations of the cold-water Muggiaea atlantica. The water in the upwelling cell around Port Alfred appears functionally distinct from Agulhas Current waters, and the high abundance of siphonophores here indicates a localised region of high production.
Collaborators: Mark Gibbons (Univ. of the Western Cape), Johann Lutjeharms (Univ. of Cape Town)
Ctenophores ecology in the Benguela region (South Africa)
This study was undertaken to investigate the importance of the ctenophore Pleurobrachia pileus in the southern Benguela region (west coast of South Africa). This region is under the influence of strong upwelling and large fisheries (sardines, anchovies) have been commercially exploited for many years. Decrease in the fisheries in the past few years might be directly (feeding on fish eggs) or indirectly (feeding on prey for fish) connected to the presence of gelatinous zooplankton (medusae, ctenophores). Here we have focused on the ctenophore Pleurobrachia pileus which is often present in high density. Its vertical distribution, abundance and size composition of a population was studied and its potential impact on zooplankton assessed. This species can remove large portion of the mesozooplankton population and at time can even remove in excess of 100% of the integrated standing stock of mesozooplankton. This species has shown also in the laboratory the capability to survive over 40 days without food and its egg production capacities can quickly response to increase in local food. Based on the collected data we are developing an individual bio-energetic model for Pleurobrachia pileus.
Collaborators: Mark Gibbons (UWC), Emmanuelle Buecher (UWC)
Gelatinous zooplankton in the Hawaiian Islands and impact on tourism and local fisheries
Up to now we do not know where/how most of the jellyfish species reached the Hawaiian Island and how far they have been spreading. Species such as Carybdea alata, a box jelly species, have been observed on few beaches of O‘ahu only for the past 10 years, and its distribution seems to have been extended further North (now reported off Kailua) and to neighbor islands. Other species such as the Portuguese man o’ war, Physalia physalis, have been a longer resident of the Hawaiian waters. The well known moon jelly, Aurelia aurita, has been observed first in Pearl Harbor, obviously brought around through ballast waters. Most of the gelatinous zooplankton can survive for long period of time without food and have the potential to reproduce/grow at very high rates. They also often show a strong adaptability to different physical/chemical conditions of their environment. They will then be able (if not already) to spread further and further away from their sources of introduction, which will be facilitate by their pelagic form and their low motility (they will be brought about by the main currents). Until a complete study of the population of gelatinous zooplankton (mainly jellyfish) can be conducted we will not know the potential threat they may have on the coral reef ecosystem of the Hawaiian Islands. Therefore we have started to run a descriptive study of the gelatinous zooplankton communities within the Hawaiian Islands coral reef ecosystem, at several selected sites (some in areas of strong human influence, some isolated, and in between situations). We will soon start studying the local impact of gelatinous zooplankton on the food web using both in situ and lab work and we are hoping to develop a surveillance array around sensitive areas where importation of new invasive species might happen.
Collaborators: Mark Huntley (UH), Mai Lopez (UH),
Gelatinous zooplankton in the Arctic Ocean
Samples collected during the AOS’94 cruise have been re-examined to look at the importance of gelatinous zooplankton in this peculiar region. Small species collected by the nets belonged to the siphonophores, medusae, chaetognath, and appendicularian taxa. Importance of these taxa will be evaluated and their potential impact on the local food web estimated.

Recent Publications: 2000 to Present

Thibault-Botha D. and M.J. Gibbons. Submitted. Biology of Abylidae (Cnidarians, Siphonophores) in the Agulhas current (South East Coast of South Africa). Marine Biology.

Thibault-Botha D. and T. Bowen. Submitted. Impact of formalin preservation on Pleurobrachia bachei (Ctenophore). Journal of Experimental Marine Biology and Ecology.

Thibault-Botha D. and M. J. Gibbons. Accepted. Common Epipelagic Siphonophores of the Agulhas Current. South African Journal of Marine Science.

Thibault-Botha D., J. R. E. Lutjeharms and M. J. Gibbons. Accepted. Siphonophore assemblages along the East Coast of South Africa. Mesoscale distribution and seasonal variations. Journal of Plankton Research.

Gibbons M.J., E. Buecher and D. Thibault-Botha, 2003. Observations on the ecology of Pleurobrachia pileus (Ctenophora) in the southern Benguela ecosystem. South African Journal of Marine Science.

Gibbons, M.J. and D. Thibault-Botha, 2002. Zoogeography and diversity of epipelagic siphonophores around southern Africa. Journal of Marine Biological Association, U.K. 82 (5): 801-810.

All publications (MS Word document)

Professional Service

American Geophysical Union (AGU)
American Society of Limnology and Oceanography (ASLO)
Jun 1999-Aug 2001: Post-Doctoral Fellow, Zoology Department, University of the Western Cape, Bellville, South Africa
Jun-Oct 1998: Post-Doctoral Research Associate contract, Oregon State University.
Aug 1995-Mar 1998: Post-Doctoral Fellow in Oceanography, National Institute of Scientific Research (INRS-Oceanology), Rimouski, Quebec, Canada.
Jun 1994-Mar 1995: Post-Doctoral contract, Oregon State University, National Science Foundation and Bedford Institute of Oceanography, Halifax, Nova-Scotia, Canada.

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