Influence of hypoxia on the distribution, behavior, and foraging of zooplankton and planktivorous fish in central Lake Erie: Field observations & future directions Hank Vanderploeg, GLERL Stuart Ludsin, GLERL Steve Pothoven, GLERL Tomas Höök, CILER Univ. of Michigan James Roberts, Univ. of Michigan Steve Ruberg, GLERL Joann Cavaletto, GLERL James Liebig, GLERL Gregory Lang, GLERL Stephen Brandt, GLERL Hypoxia is an old problem in freshwater—Results for Cyclops bicuspidatus (Einsle 1965) This species is very tolerant of low oxygen (~ 0.1mg/L) Original Lake Erie Fish-Centric Hypotheses 1. Hypoxia will disrupt vertical migration behavior – Reduce time spent on bottom 2. Hypoxia will influence horizontal movement – Fish will move into oxygenated, shallow nearshore zones 3. Hypoxia will reduce availability of prey, both ZP & benthic macroinvertebrate prey – ZP use hypoxia as a refuge from predation – Hypoxia reduces benthic prey abundance 4. Fish consumption & condition will decline Playing chess with death—a zooplankton-centric view Scene from Bergman’s “The Seventh Seal” Death normally comes in two forms: predation and starvation • Zooplankton vertical migration is strategy to minimize overlap with visually preying invertebrate and vertebrate (fish) predators— conspicuous or unprotected (spineless) zooplankton move to lower light levels • Move into upper favorable (temperature and food) areas at night. • Predator abundance is assessed by kairomones. • When many predators, the zooplankter (prey) must play chess to avoid overlap. The Great Lakes have both visual invertebrate & and vertebrate predators—Lake Michigan example Playing chess with death—the piscine players Scene from Bergman’s “The Seventh Seal” Dominant planktivores of Lake Erie and their Vanderploeg & Scavia (1979) selectivity coefficients (W´) pre-hypoxia Emerald Shiner August 2005 Emerald shiner: Epilimnetic planktivore 1.00 W' 0.75 Night 0.50 Day 0.25 Si Bo sm in id ae di da e Cy clo po id Da ph ni da Ca e la no Ch id yd or id ae Le pt od By or th a ot re Ch ph es iro m om id ae 0.00 Rainbow Smelt August 2005 1.00 W' 0.75 Night 0.50 Rainbow Smelt: Planktivore-benthivore Day 0.25 di da Cy e clo po id a Da ph ni da e Ca la no id Ch a yd or id ae Le pt od By or th a ot re Ch ph es iro m om id ae Si Bo sm in id ae 0.00 Prey size USGS-NAS Hypoxia, another form of death, alters the game—some hypotheses: • Differential tolerance of zooplankton to hypoxia allows some species to enter the hypoxic zone to escape predators—the refuge • Others will be forced out and trapped in lighted areas above—the hypoxia-light trap. Lake Erie Some results before and after major hypoxia will give us some insights 43 Diel Station B 42.5 12 42 41.5 43 -83.5 August -82.5 -81.5 -80.5 -79.5 42.5 9 6 3 42 41.5 -83.5 September -82.5 -81.5 -80.5 -79.5 0 Dissolved Oxygen (mg/l) General Methods—What we did Introduction to Study Systems & General Methods • Zooplankton • Temperature • Dissolved oxygen • Light levels • Chlorophyll a Fish Biomass • Trawling (fish species & samples for diet & ration work) • Zooplankton net and pump sampling (zooplankton) • Ponar sampling (benthic macroinvertebrates) Lake Erie Field Program (IFYLE 2005) EPA-GLNPO R/V Lake Guardian (180’) Source: Don Coles NOAA-GLERL R/V Laurentian (80’) Diel Station B Transect B Diel (24-hr) Transect (day-night) Water Column Pumping Method shooting for pumping 1 cubic meter of water 0 5 10 15 20 0 Sept. 2005 2 4 6 o Water Temp ( C) 1 min. ea. depth DO (mg/L) Depth (m) 8 10 12 14 1 min. ea. depth 16 5 min.ea. 18 20 22 24 2 min. ea. depth 25 Lake Erie Ho 2: Hypoxia will alter horizontal distribution of abundance – Fish will move into oxygenated, shallow nearshore zones 43 42.5 August 42 41.5 -83.5 43 42.5 Transect B -82.5 -81.5 -80.5 -79.5 September 9 6 42 41.5 -83.5 43 42.5 12 3 -82.5 -81.5 -80.5 -79.5 0 October 42 41.5 -83.5 -82.5 -81.5 -80.5 -79.5 Dissolved Oxygen (mg/l) Lake Erie Ho 2: Hypoxia will alter horizontal distribution of abundance (August – Pre-Hypoxia) 0 Night 0 Day 30 22 10 10 14 20 20 Depth (m) 0 Temp (º C) 41.7 41.8 41.9 42 42.1 0 41.7 41.8 41.9 42 42.1 12 9 10 10 6 6 20 20 0 0 41.7 41.8 41.9 42 42.1 10 3 41.7 41.8 41.9 42 42.1 0 -30 -50 10 -70 20 41.8 41.9 42 42.1 Fish (dB) -90 20 41.7 DO (mg/l) 41.7 41.8 41.9 42 42.1 -110 Latitude (degrees)Ludsin, Vanderploeg & Ruberg, unpub Lake Erie Ho 2: Hypoxia will alter horizontal distribution of abundance (September – Peak Hypoxia) 30 0 0 Day Night 10 22 10 Depth (m) 14 20 20 0 0 41.7 41.8 41.9 42 42.1 6 41.7 41.8 41.9 42 42.1 12 9 10 10 6 20 20 0 0 41.7 41.8 41.9 42 42.1 10 41.7 41.8 41.9 42 42.1 0 -30 -50 -70 41.8 41.9 42 42.1 Fish (dB) -90 20 41.7 DO (mg/l) 3 10 20 Temp (º C) 41.7 41.8 41.9 42 42.1 -110 Latitude (degrees)Ludsin, Vanderploeg & Ruberg, unpub Lake Erie Ho 2: Hypoxia will alter horizontal distribution of abundance – Reject: Fish move into oxygenated waters, but offshore (October – Post Hypoxia) 0 0 Day 10 30 Night 22 10 14 20 Depth (m) 0 20 41.7 41.8 41.9 42 42.1 0 6 41.7 41.8 41.9 42 42.1 12 9 10 10 6 20 20 0 0 41.7 41.8 41.9 42 10 42.1 41.7 41.8 41.9 42 42.1 0 -30 -50 -70 20 41.6 41.7 41.8 41.9 DO (mg/l) 3 10 20 Temp (º C) Fish (dB) -90 41.6 41.7 41.8 41.9 -110 Latitude (degrees)Ludsin, Vanderploeg & Ruberg, unpub Playing chess with death—Insights from pre-hypoxia (control) & hypoxia distributions and prey selection Scene from Bergman’s “The Seventh Seal” Diel B, Aug 17, 01:00 EDT PAR 0 100 200 300 400 500 0 Fish biomass (relative) Depth (m) 5 Zoomass (10 ug/L) Chl (ug/L) 10 DO (mg/L) 15 Temp ('C) 20 PAR (uE/m2/s) 25 0 5 10 15 Chl, DO, Zoop, Temp 20 25 Diel B, Aug 17, 13:00 EDT PAR 0 200 400 600 800 1000 1200 0 Fish biomass (relative) Depth (m) 5 Zoomass (10 ug/L) Chl (ug/L) 10 DO (mg/L) 15 Temp ('C) 20 PAR (uE/m2/s) 25 0 5 10 15 Chl, DO, Zoop, Temp 20 25 Lake Erie B 8-17-05 DIEL 02:00 Copepods mg . m-3 0 10 20 30 40 Cladocerans mg . m-3 0 100 200 Predatory Cladocerans mg . m-3 0 10 20 0 4 Diacyclops Mesocyclops Tropocyclops Diaptomids Epischura nauplii Bosmina Eubosmina Daphnia mendotae D. longiremis Leptodora Bythotrephes Cercopagis EPI depth 8 12 META 16 20 HYPO 4.8 mg/L DO 24 4.8 mg/L DO 4.8 mg/L DO 30 Lake Erie B 8-17-05 DIEL Cladocerans mg . m-3 Copepods mg . m-3 0 50 100 0 20 40 14:00 Predatory Cladocerans mg. m-3 0 1 0 4 Diacyclops Mesocyclops Tropocyclops Diaptomids Epischura nauplii depth 8 Bosmina Eubosmina Daphnia mendotae D. longiremis D. retrocurva Leptodora Bythotrephes EPI 12 META 16 20 HYPO 4.8 mg/L DO 24 4.8 mg/L DO 4.8 mg/L DO 2 Diel B, Sept 18, 03:00 EDT PAR 0 100 200 300 400 500 0 Fish biomass (relative) Depth (m) 5 Zoomass (10 ug/L) Chl (ug/L) 10 DO (mg/L) 15 Temp ('C) 20 PAR (uE/m2/s) 25 0 5 10 15 20 Chl, DO, Zooplankton, Temp 25 Diel B, Sept 17, 15:00 EDT 0 100 200 PAR 300 400 500 0 Fish biomass (relative) Depth (m) 5 Zomass (10 ug/L) Chl (ug/L) 10 DO (mg/L) 15 Temp ('C) 20 PAR (uE/m2/s) 25 0 5 10 15 20 Chl, DO, Zooplankton, Temp 25 Lake Erie B 9-18-05 DIEL 02:00 . -3 . Copepods mg m 0 100 200 Cladocerns mg m 0 20 40 60 -3 80 . Predatory Cladocerans mg m 0 1 2 0 depth 4 Diacyclops Mesocyclops Tropocyclops Diaptomids Epischura nauplii Bosmina Eubosmina Daphnia mendotae D. longiremis D. retrocurva Diaphanasoma 8 upper epi 12 lower epi Leptodora 16 meta 20 hypo 1.2 mg/L DO 24 1.2 mg/L DO 1.2 mg/L DO -3 3 Lake Erie B 9-17-05 DIEL 14:00 . -3 . Copepods mg m 0 20 40 60 80 -3 Cladocerans mg m 0 20 40 . 0.0 0.5 0 4 Diacyclops Mesocyclops Tropocyclops Diaptomids Epischura nauplii depth 8 Bosmina Eubosmina Daphnia mendotae D. longiremis D. retrocurva Diaphanasoma Leptodora upper epi lower epi 12 16 meta 20 hypo 1.2 mg/L DO 24 1.2 mg/L DO -3 Predatory Cladocerans mg m 1.2 mg/L DO 1.0 Selectivity coefficient of Vanderploeg & Scavia (W´) for Emerald shiner and Rainbow Smelt in August 2005 Emerald Shiner August 2005 Emerald shiner: Epilimnetic planktivore 1.00 W' 0.75 Night 0.50 Day 0.25 Si Bo sm in id ae di da e Cy clo po id Da ph ni da Ca e la no Ch id yd or id ae Le pt od By or th a ot re Ch ph es iro m om id ae 0.00 Rainbow Smelt August 2005 1.00 W' 0.75 Night 0.50 Rainbow Smelt: Planktivore-benthivore Day 0.25 di da Cy e clo po id a Da ph ni da e Ca la no id Ch a yd or id ae Le pt od By or th a ot re Ch ph es iro m om id ae Si Bo sm in id ae 0.00 Prey size USGS-NAS Selectivity coefficient of Vanderploeg & Scavia (W´) for emerald shiner and rainbow smelt in September 2005 Emerald Shiner September 2005 Emerald shiner: 1.00 Epilimnetic planktivore W' 0.75 Night 0.50 Day 0.25 di da e Cy clo po id Da ph ni da Ca e la no Ch id yd or id ae Le pt od By or th a ot re Ch ph es iro m om id ae Bo sm Si in id ae 0.00 Rainbow Smelt September 2005 1.00 Night 0.50 Day 0.25 po id a Da ph ni da e Ca la no id Ch a yd or id ae Le pt od By or th a ot re Ch ph es iro m om id ae di da e Cy clo Si in id ae 0.00 Bo sm W' 0.75 Rainbow smelt: Planktivore-benthivore Prey size USGS-NAS What’s going on down there? Present status: Heavy emphasis in IFYLE Hypoxia study on upper food web (fish and location of fish food) We do know, however: • Mesozooplankton and microzooplankton distribution relative to hypoxia response is species specific • Microzooplankton grazing dominates during the summer • Bacteria-based food web becomes important in hypoxic zone What’s going on down there? For the development of a conceptual framework we’d like to know: • What is the minimum oxygen concentration a zooplankter (species by species) is willing to enter yet survive under various predation risk scenarios? • How does feeding and behavior vary with oxygen concentration? • What is the joint distribution of meso-and microzooplankton around hypoxic zones • How is production and predation risk affected? We know something about Daphnia foraging in hypoxic areas but nothing for copepods, the dominants in the Great Lakes, or for visual invertebrate predators From Heisey & Porter (1977) Some possible lab approaches to define spatial rules of food web assembly (“indirect effects”) • Observe location of position of zooplankton in laboratory water columns with gradients of light, temperature, kairomones of potential predators & oxygen • Directly observe behavior and foraging in hypoxic water columns. • Observe effect of hypoxia on visual predation (both invertebrate & vertebrate)—have predators watch TV Inside the lab Outside the lab: keeping the predator in focus