|Geange, Shane||Victoria University of Wellington||Principal Investigator, Contact|
|Shima, Jeffrey||Victoria University of Wellington||Co-Principal Investigator|
|Stier, Adrian||University of Washington (UW)||Co-Principal Investigator|
|Biddle, Mathew||Woods Hole Oceanographic Institution (WHOI BCO-DMO)||BCO-DMO Data Manager|
This dataset is from a manipulative experiment to investigate how nudibranchs and sea hares alter cyanobaterica production through a trophic cascade. This research was conducted in 2008 at the Gump Biological Research Station, Moorea, French Polynesia. For additional data, please see files listed in Related Datasets.
All experiments were conducted in plastic containers (190 mm x 190 mm x 90 mm; W x L x H). To allow the exchange of fresh seawater, approx. 80% of the surface area of the lids, and two opposing sides of containers were cut away and covered with 0.5 mm mesh screening. Containers were placed within large (2,670 l) outdoor flow-through seawater tanks (10 containers per tank). In each experiment, sea hares (Stylocheilus striatus), nudibranchs (Gymnodoris ceylonica), and cyanobacteria (Lyngbya spp.) were collected from the field. Prior to experiments, nudibranchs were starved for 3 days, and cyanobacteria were rinsed with filtered seawater, which removed associated flora or fauna.
The presence of a trophic cascade was examined using three treatments: (1) cyanobacteria alone (n = 16); (2) cyanobacteria and sea hares (n = 8); (3) cyanobacteria, sea hares, and nudibranchs (n = 8). Cyanobacteria (mean = 78.0 g, SD = 12.9) were added to each of the 32 containers. Ten sea hares (mean length 57.4 mm ± 5.6 SD) were added to containers assigned to treatments 2 and 3, and one nudibranch (mean length 48.6 mm ± 3.6 SD) was added to containers assigned to treatment 3. Each morning (*0700), the number of surviving sea hares in each container was recorded. Nudibranch densities were maintained at their original density by replacing any missing or dead nudibranchs throughout the duration of the study (two nudibranchs were replaced on day two, and no other replacements were necessary). After 4 days, cyanobacterial biomass (g) and the number of sea hares in each container were recorded.
|Date||Date of Experiment (in yyyymmdd format)||unitless|
|OBS||Name of observers (SWG (Shane Geange) or ACS (Adrian Stier))||unitless|
|bin||Unique container ID||unitless|
|initial_alg||Initial weight of algae (g)||grams (g)|
|final_alg||final weight of algae (g)||grams (g)|
|delta_mass||initial_alg - final_alg||grams (g)|
|pred_ttt||Nudibranch presence or absence||unitless|
|aplysia||Sea hare presence or absence||unitless|
|initial_aplysia||Initial number of sea hares at the start of experiment in each container||unitless|
|final_aplysia||Final number of sea hares at the end of the experiment||unitless|
|prop_surv||Proportional survival of sea hares at the end of the experiment. Proportion survival was calculated as final_aplysia/initial_aplysia.||unitless|
Osenberg et al Moorea
|Start Date|| |
|End Date|| |
Description from NSF award abstract:
Ecologists have long been interested in the factors that drive spatial and temporal variability in population density and structure. In marine reef systems, attention has focused on the role of settlement-the transition of pelagic larvae to a benthic stage-and on density-dependent processes affecting recently settled juveniles. Recent data suggest that co-variance in settlement and subsequent density-dependent survival can obscure the patterns of density dependence at larger scales, a phenomenon called cryptic density dependence. This research will explore the mechanisms that underlie the spatial covariance of settlement and site quality - a process that has received little attention in the standard paradigm. These mechanistic studies of cryptic density dependence will facilitate the development of new frameworks for fish population dynamics that incorporate larval ecology, habitat quality, density dependence, life history, and the patterns and implications of spatial covariance among these factors. More generally, the work provides a specific empirical context, and a general theoretical treatment, of cryptic heterogeneity (hidden individual variation in demographic rates).
Note: Drs. Craig W. Osenberg and Ben Bolker were at the University of Florida at the time the NSF award was granted. Dr. Osenberg moved to the University of Georgia during the summer of 2014 (current contact information). Dr. Bolker moved to McMaster University in 2010 (current contact information).