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Why do biological oceanographers care about planktonic protozoa (i.e., microzooplankton)? And why should the microbial loop be included in models of pelagic.

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Presentation on theme: "Why do biological oceanographers care about planktonic protozoa (i.e., microzooplankton)? And why should the microbial loop be included in models of pelagic."— Presentation transcript:

1 Why do biological oceanographers care about planktonic protozoa (i.e., microzooplankton)? And why should the microbial loop be included in models of pelagic ecology?? Dian J. Gifford Graduate School of Oceanography University of Rhode Island Narragansett, RI, USA

2 Classical Linear Food Chain Phytoplankton Zooplankton Fish D.J. Gifford Imaging Laboratory Graduate School of Oceanography University of Rhode Island

3 Phytoplankton Microbial Food Web Metazoan Food Web CO 2 DOC Protozoa Bacteria Zooplankton ? POC ? (Sherr & Sherr 1988) D.J. Gifford Imaging Laboratory Graduate School of Oceanography University of Rhode Island Fish

4 Major Taxa Nanozooplankton (2-20  m): Microzooplankton (  m): Heterotrophic flagellates Ciliates Heterotrophic dinoflagellates Ciliates Heterotrophic dinoflagellates D.J. Gifford Imaging Laboratory Graduate School of Oceanography University of Rhode Island

5 Ecological Functions of Planktonic Protozoa Primary Production : retention of functional chloroplasts; mixotrophy Nutrient Cycling : excretion fuels water column primary production Grazing : major source of phytoplankton and bacterial mortality Trophic Coupling : prey of higher trophic levels D.J. Gifford Imaging Laboratory Graduate School of Oceanography University of Rhode Island

6 Ciliates Containing Plastids or Endosymbionts D.J. Gifford Imaging Laboratory Graduate School of Oceanography University of Rhode Island

7 Contribution to Water Column Photosynthesis D.J. Gifford Imaging Laboratory Graduate School of Oceanography University of Rhode Island (Stoecker et al. 1990)

8 Log Dry Weight (mg/organism) Nitrogen Excretion Rate (ug N/mg Dry Weight/d) Protozoa Metazoan Zooplankton (Caron 1991) D.J. Gifford Imaging Laboratory Graduate School of Oceanography University of Rhode Island

9 GRAZING d [Chl]u [Chl]u ( k - a - m - s - g + x ) ~ 0 dt = cell division advection mixing sinking grazing horizontal terms D.J. Gifford Imaging Laboratory Graduate School of Oceanography University of Rhode island Imaging Laboratory Graduate School of Oceanography University of Rhode Island (Banse, 1992)

10 Protozoan Grazing Impact in Pelagic Ecosystems D.J. Gifford Imaging Laboratory Graduate School of Oceanography University of Rhode Island

11 AugustSeptemberJanuary Microplankton prey category Clearance rate (ml/copepod /h) Ingestion rate (ngC/copepod/h) Chla Acartia tonsa Dana Coastal Gulf of Mexico Gifford and Dagg, 1988

12 Neocalanus plumchrus Marukawa Ingestion rate (ug C/copepod/d) Ciliates Het. dionflagellates > 20 um Radiolarians Het. flagellates & dinoflagellates < 20 um Phytoplankton Total Mean ingestionMaximum ingestion Subarctic North Pacific Gifford, 1993

13 Crest Southern Flank Northeast Peak Jan Feb/Mar Apr May June PhytoplanktonProtozooplankton Fraction Body C Ingested /d 0.5 Georges Bank Calanus finmarchicus Gifford and Sieracki, submitted

14 Ingestion Rate (ug C/copepod/d) 22 Jan 26 Feb14 Apr 24 Jun 9 Jul23 Jul20 Aug Strong upwelling Relaxed upwelling Fessenden and Cowles, 1994 Coastal Oregon

15 Chemical Composition Taxon C:N Reference Phytoplankton 6Parsons et al Heterotrophic flahgellates4 - 7Goldman et al Borsheim & Bratbak 1987 Tintinnid ciliates4 - 5Verity & Langdon Stoecker & Sanders 1985 Oligotrich ciliates Mixotrophs4 - 8Putt & Stoecker 1989 Heterotrophs3 - 4Putt & Stoecker 1989

16 Chemical Composition Chemical Constituent Taxon Reference Lipids PUFAsCiliates Aaronson & Baker 1961 Kaneshiro et al Holz & Conner 1987 H dinoflagellates Harrington & Holz 1968 H flagellates Holtz & Connor 1987 Fatty acids H dinoflagellates Holtz & Connor 1987 H flagellates Holz & Connor 1987 Ciliates Sul & Erwin 1998 SterolsCiliates Harvey et al H flagellates Alam et al FAAs Ciliates Kaneshiro et al Starch H dinoflagellates Holz & Connor 1987 Ciliates Johnson et al. 1995

17 Significance: Effects on Consumers EffectConsumerPreyReference Enhanced survival Eurytemora affinisCiliatesBerk et al Daphnia pulexCiliatesWickham et al Daphnia magnaCiliates + HflagellatesDiBiase et al Increased growth rate Megacyclops sp. naupliiHflagellatesAbdullahi 1992 Artemia salinaCiliates + HflagellatesSeki 1964 Increased reproduction Acartia tonsaCiliatesStoecker & Egloff 1987 H dinoflagellatesKleppel & Burkart 1995 Eurytemora affinisCiliatesHeinle et al Acartia clausiH dinoflagellatesBreteler et al. 1980

18 Significance: Effects on Prey Populations Prey Population ConsumerCleared / day(%)Reference Eurytemora affinis100Sheldon et al Acartia sp., Oithona sp.50Nielsen & Kiorboe 1981 Acartia tonsa34-200Dolan 1991 Artemia franciscana99Wurtsbaugh 1992 Neocalanus plumchrus10-26Gifford & Dagg 1991 Synchaeta littoralis80Arnat 1993

19 Mesozooplankton Taxa Feeding on Microzooplankton Suspension Feeding Copepods Acartia clausi (Ayukai 1987; Wiadnyana & Rassoulzadegan 1989; Broglio et al. 2001) Acartia hudsonica (Wiadnyana & Rassoulzadegan 1989) Acartia longiremis (Levinson et al. 2000) Acartia spp. (Batten et al. 2001) Acartia tonsa (Robertson 1983; Gifford & Dagg 1988; Stoecker & Egloff 1989; Jonsson & Tiselius 1990) Calanus finmarchicus (Gifford, submitted; Levinson et al. 2000) Calanus glacialis (Levinson et al. 2000) Calanus hyperboreus (Levinson et al. 2000) Calanus pacificus (Fessenden & Cowles 1994) Calanus propinquus (Atkinson 1995) Calanus spp. (Batten et al. 2001) Centropages typicus (Wiadnyana & Rassoulzadegan 1989) Centropages cherchiae (Batten et al. 2001) Centropages abdominalis (Fessenden & Cowles 1994) Clausocalanus spp. (Batten et al. 2001) Eucalanus pileatus (Verity & Paffenhofer 1996) Eurytemora affinis (Berk et al. 1977) Metridia gerlachei (Atkinson 1995) Neocalanus plumchrus (Gifford 1993) Neocalanus tonsus (Zeldis et al. 2002) Oithona spp. (Atkinson 1995) Pseudocalanus sp. (Fessenden & Cowles 1994) Para-pseudocalanus spp. (Batten et al. 2001) Decapod larvae Hemigrapsis sanguinea (Gifford & O’Connor, unpubl.) Cancer magister (Sulkin et al. 1998) Miscellaneous crustaceans Balanus cf. Crenatus nauplii (Turner et al. 2001) Freshwater cladocera (Wickham & Gilbert 1991; Pace & Vaque 1994; Wiakowsji et a. 1994; Adrian & Schneider-Olt 1999) Bivalves Crassostrea gigas (Dupuy et al. 1999) Gelatinous zooplankton Aurelia aurita (Stoecker et al. 1987) Mnemiopsis leidyi (Stoecker et al. 1987; Sullivan & Gifford, submitted) Larval fish Theragra chalcogramma (Lessard et al. 1996; Nishiyama & Hirano 1985) Gadus morhua (Von Herbing & Gallager 2000))

20 Chl a

21 Globec 01: Patterns of Energy Flow and Utilization on Georges Bank Funding: National Science Foundation: $1,500,000 Timeline: Principal Investigator: Dian Gifford, University of Rhode Island Co-Investigators: James Bisagni, University of Massachusetts Jeremy Collie, University of Rhode Island Edward Durbin, University of Rhode island Michael Fogarty, NMFS, Woods Hole Jason Link, NMFS, Woods Hole Lawrence Madin, Woods Hole Oceanographic Institution David Mountain, NMFS, Woods Hole Debra Palka, NMFS, Woods Hole Michael Sieracki, Bigelow Laboratory for Ocean Science John Steele, Woods Hole Oceanographic Institution Barbara Sullivan, University of Rhode island

22 General Objective: To provide a broad ecosystem context for interpretation of the population dynamics of Georges Bank GLOBEC target species. Specific Objectives: Examine alternate model outcomes of GLOBEC and GLOBEC-related studies Examine the mechanisms forcing changing patterns of energy flow on Georges Bank With explicit consideration of factors not addressed in earlier models of the system: Sources and fates of new production The role of the microbial food web in production processes Secondary production processes, including the apparent secondary production deficit Changes in invertebrate and vertebrate predator species composition in the context of population dynamics of GLOBEC target organisms Effects of environmental forcing on production processes during contrasting (~decadal) time periods

23 Scientific approach: (1) Combine top-down [consumption-based models] and bottom-up [production-based models] approaches to describe Georges Bank food web (2) Use these analyses as a precursor to dynamic modeling Principal tools:  Linear network analysis (Vezina, 1999; 2000)  Nonlinear dynamical modeling (Collie and Delong 1999). Focus on two major issues: (1) Imbalance between primary production and fish production. “leakage hypothesis” v. microbial web dynamics (2) Magnitude of top-down [fish] v. bottom-up [microbial web] processes

24 Locations of three spatial domains on Georges Bank derived from an EOF mode 1 SST map (Bisagani et al. 2000). GBC=Georges Bank Crest. TMF = Tidal Mixing Front. GBSF = Georges Bank Southern Flank. Spatial domains change with season.

25 A B A. Spring (open bars) and fall (filled bars) bottom temperature anomalies for Georges Bank. The data are from NMFS spring ( ) and fall ( ) trawl surveys. The anomalies are referenced to the MARMAP data set ( ). B. Spring (open bars) and fall (filled bars) salinity anomalies for Georges Bank. The data are from NMFS spring ( ) and fall ( ) trawl surveys. The anomalies are referenced to the MARMAP data set ( ). Temperature Salinity

26 Changes in fish abundances on Georges Bank since the 1960s (Collie and Delong, 1999):  Decreasing gadoids and flatfish  Increasing pelagics and elasmobranchs

27 Temporal Stanzas: three time periods are defined on the basis of the historical temperature record: Seasons: three seasons are defined on the basis of mixing regime: September-April: well-mixed April-June: episodic stratification June-September: stratified

28 Pre-Recruit Fish Demersal Fish Pelagic Fish Pelagic Microbial Food Web Vertebrate Predators Small Invert Predators Meso- Zooplankton (>200 um) Benthic Food Web Macro- Benthos Meio- Benthos Nano- and Micro-- Phytoplankton Nano-- Zooplankton (<20 um) Micro- Zooplankton ( um) Bacteria Detritus NO3 Physics + Climate Elasmobranch Fish Birds & Mammals Pelagic Metazoan Food Web Large Invert Predators Invertebrate Predators

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