AT42-13: Cowen "Mesozooplankton Food Webs"

Ship

Cruise Party

Departure: Jul 15, 2019

Arrival: Jul 26, 2019

Operations Area

Science Objectives

MEsoZooplankton trophodynamics in the CALifornia Current (MEZCAL)

General approach

Our overall approach is to sample the summer trophic web off the coast of Newport, OR and Trinidad, CA. Cruise data will be combined with a winter and summer cruise from 2018 and this year's winter cruise in order to investigate differences in the activity of the traditional food web as well as the microbial foodweb with regard to season (summer/winter) and upwelling (continuous off the coast of CA and intermittent off OR). For that we sample with a high resolution in situ plankton imaging device (In Situ Ichthyoplankton Imaging System, ISIIS) to obtain an accurate description of plankton communities: their abundances, patchiness, and horizontal and vertical spatial distributions. In parallel, we collect depth-discrete mesozooplankton samples to quantify diets for larval fishes and gelatinous zooplankton and prey-specific growth rates of larval fishes.

Science Activities

This is the fourth of four research cruises in the NCC. Cross-shelf transects will be located off of (1) Newport, OR and (2) Trinidad Head, CA to capitalize on historic records of ocean conditions.

We will deploy ISIIS along transects from East to West during daylight hours and then West to East at night. Traversing the transect again, we will sample as many of the stations as possible with a coupled MOCNESS from East to West in daylight hours, and then we do as many stations as possible again on the way back from West to East, during night time. Sampling is adaptive and follows marine dawn and sunset. We also deploy a ½ m diameter ring net down to 25 m before or after each MOCNESS deployment.

To collect water samples for Particulate Organic Matter (POM) we will utilize CTD/Niskin bottle deployments at each MOCNESS station during the daylight transect. This complete sampling of a transect with ISIIS, MOCNESS, ring nets, and CTD will take 48 hrs. We will repeat this sampling of the transect off Oregon, taking another 48 hrs, and then transit (24 hrs) to the northern CA site and repeat the same sampling regime (96 hrs total) on the onshore-offshore transect off Trinidad Head, CA. The ship will need a final 24 hrs to return to Newport following the CA sampling, resulting in a total at-sea cruise time of 10 days.

Sampling technology: 

In Situ Ichthyoplankton Imaging System (ISIIS)– Our central sampling technology is the In Situ Ichthyoplankton Imaging System (ISIIS), a high resolution imaging system designed to image sufficient volumes of water to accurately quantify rare meso- and macroplankton such as larval fishes and gelatinous zooplankton in situ). The current system (ISIIS-2) consists of two separate cameras: the first capable of imaging up to 140 L s^-1, with pixel resolution of 68 µm, and the second, small camera capable of imaging to 35 µm pixel resolution. Together, the dual camera system enables resolution of in situplanktonic taxa from large ciliates to medusae. The ISIIS is also instrumented with a set of environmental sensors including: CTD, PAR, O₂, and fluorometry. All data are passed via fiber optic cable to an onboard computer, time-stamped for cross-referencing, and saved on a high-speed disk array (also experimental Amazon snowball setup as discussed on this cruise). The line-scan cameras build continuous images; if the instrument is towed for 100 km, it has a 100-km long image with 68-µm or 35-µm line (pixel) resolution. Thus, ISIIS can assess distributions ranging from cm to 10s of km (or more if the instrument is towed farther).

 For the ISIIS we will bring a Hawblodt 0.322 fibre optic winch from the WHOI winch pool with us. 

Coupled Multiple Opening and Closing Net and Environmental Sampling System (coupled MOCNESS)– To sample a range of zooplankton simultaneously, we will use a coupled MOCNESS system consisting of a 4m²net fitted with 1 mm mesh and a 1 m²net with 333 µm mesh. A series of five paired nets that can be remotely triggered to open and close will enable us to sample different depths discretely. MOCNESS samples will be used to validate and compare to ISIIS imagery, but primarily to collect biological specimens for analysis of diet (gut contents), growth (larval fish otolith microstructure), fatty acids, and stable isotopes composition. Immediately after collection, a sub sample of each net sample will be sorted for common gelatinous zooplankters for diet analysis and then preserved individually in 5% buffered formalin. The remaining contents of all samples will be fixed and preserved in 70% ethanol. Net 0 samples are integrated across all depths as this net is open on initial deployment to depth. To provide direct comparison of MOCNESS sampling to existing time series sampling along these two historical transect lines, we will also deploy the standard vertical ring net casts at each day station. All biological samples are either stored in ethanol, formalin, or frozen in the -80C freezers, no fatty acid or stable isotope analyses will be processed on board.

 For MOCNESS we will rely on one of your ship winch systems, please.

Additional Info

Stations:

Supporting documentation:

Shipboard Equipment

Shipboard Communication

CTD/Water Sampling

Critical CTD Sensors

MET Sensors

Sample Storage

Navigation

Navigation

Winches

Wire use and application

Standard Oceanographic Cables

Specialized Deck Equipment

Over the Side Equipment

Special Requirements

Additional Cruise Items/Activities

Hazardous Material

Radioactive Material

Additional Information

Checklist

Checklist