Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Data Files
• Related Publications
• Parameters
• Instruments
• Project Information
• Funding

This dataset reports the chlorophyll-a concentrations for polyunsaturated aldehydes (PUA) experiments with samples from Virginia Coastal Bays and Bay of Napoli.

Experiments were conducted by collecting raw seawater, filtering it through 200µm mesh sieves into 20L carboys, and then dispensing it into experimental jars. Triplicates bottles were used for each treatment. Treatments included whole seawater (control), whole seawater plus copepods (Zooplankton), and the same treatments plus PUA additions (Heptadienal, Octadienal, Decadienal, and Mixed PUA). PUA were dissolved in methanol and added to experimental bottles for a final concentration of 21 nM; for the mixed PUA treatment this was 7nM of each type of PUA.

Initial samples were collected from the carboy for chlorophyll a as described below. Final samples were collected from each treatment and control bottle as described below.

Chlorophyll a samples (50-150ml) were filtered onto 25mm diameter GF/F filters (nominal 0.7 micrometer pore size), and filters were extracted in 90% acetone at -20 degrees C for 24 hours using the acid method (EPA Method 445 - Arar & Collins 1997), then analyzed on a Turner Designs AU10 or TD700 fluorometer.

All data were processed in Microsoft Excel.

BCO-DMO Processing Notes:
- added conventional header with dataset name, PI name, version date
- reduced some Chl_a values to 6 decimal places

Description from NSF award abstract:
This project will conduct a set of field/laboratory experiments to address the following hypotheses with respect to microzooplankton (consumers between 20-200 um) and diatom- produced polyunsaturated aldehydes:
I. Aldehydes will impair microzooplankton herbivory on diatoms and non-diatom phytoplankton.
II. Aldehydes will reduce the growth rates of microzooplankton and non PUA-producing phytoplankton.
III. In the presence of aldehyde-producing diatoms, copepods will switch to microzooplankton, whereas non- (mildly)- toxic diatoms will be an important food source for copepods.
IV. The effects of aldehydes on microzooplankton and copepods will depend on the grazers' prior exposure to PUA.

The experiments will include natural plankton, captured copepods, cultured Skeletonema marinoi (SM), including its aldehyde-producing strain, and synthetic aldehydes. To gain insights into complex interactions within planktonic communities, detailed information on their composition, abundance, and dynamics will be obtained using microscopy, flow-cytometry, and cytological methods. This approach will allow the PIs to draw conclusions about the role of diatom-produced aldehydes in phytoplankton-microzooplankton- copepod trophic interactions. The PIs will coordinate efforts and exchange information with the PUA study group at the Stazione Zoologica Anton Dohrn (Naples, Italy).

Diatoms are dominant autotrophic plankton in the ocean. Recent evidence indicates that microzooplankton are the dominant herbivores, whereas copepods often rely on microzooplankton as food, except during peak diatom production. The ability of microzooplankton to feed on large diatoms and grow as fast as their algal prey leads to the question of what allows diatoms to escape microzooplankton grazing control during the initial phases of their blooms and maintain the blooms until nutrient resources are depleted? Allelopathy is wide spread among phytoplankton. The cosmopolitan bloom-forming SM produces several aldehydes and has become a model organism in plankton allelopathy studies. Most studies on diatom cytotoxicity have been dedicated to inhibitory effects on reproduction and development of marine invertebrates, whereas surprisingly little information exists on its impact on key diatom grazers, microzooplankton. Preliminary results in the Chesapeake Bay show that aldehydes may induce cascading effects within planktonic communities. The proposed study will: (1) Improve our knowledge of the critical diatom-microzooplankton-copepod links in the coastal ocean; (2) Generate novel data on the effects of allelopathy on marine food webs; (3) Contribute to our understanding of broader patterns of marine ecosystems by comparing plankton structure and dynamics in the temperate Atlantic waters; (4) Advance biological oceanography through international collaboration.