OC473

Ship

Cruise Party

Departure: Aug 7, 2011

Arrival: Sep 1, 2011

Operations Area

Science Objectives

The impact of ocean acidification on marine ecosystems is increasingly appreciated as an urgent societal concern. Thecosome pteropods are a group of planktonic molluscs (i.e., ‘pelagic snails’) widely distributed in coastal and open ocean ecosystems of the world’s oceans. These animals form an aragonite shell, and thus are highly sensitive to ocean acidification due to the water column’s changing carbonate chemistry, and particularly the shoaling of the aragonite compensation depth at which seawater becomes corrosive to aragonite. In many regions, however, relatively little is known about the ecology of these animals.

The primary objective of the proposed work is to quantify the distribution, abundance, species composition, shell condition, and vertical migratory behavior of oceanic thecosome pteropods in the northwest Atlantic and northeast Pacific, and correlate these quantities to hydrography and concurrent measurements of carbonate chemistry, including vertical and horizontal distributions of aragonite saturation.

The first cruise of this project will be to the northwest Atlantic on the Oceanus in August 2011. A combination of underway data collection and station activities will be conducted along a transect spanning 15 degrees of latitude (35 to 50 N), employing 6 instrument packages:

1. A 1-m2 MOCNESS plankton net system

2. A profiling Video Plankton Recorder / CTD package, including bottles for water sampling.

3. A deep (500m) towed broadband acoustic scattering system

4. A hull-mounted narrowband multi-frequency acoustic scattering system. It is possible that the hull-mounted transducers will suffer from noise when the vessel is underway and so as a backup we will have a surface-towed sled with a backup complement of transducers.

5. An underway multi-parameter inorganic carbon analyzer

6. A suite of chemistry-related instruments including a DIC auto-analyzer for discret bottle sample analysis; an alkalinity auto-titrator for bottle analysis; an Agilent spectrophotometer for discrete pH measurement.

Science Activities

Departing from Woods Hole, we will set a course for the transect start point at 35N 52W. Test deployments of the instrument packages will be conducted over the continental shelf and at the shelf break, near the 200, 500, and 1000m isobaths. The transect will run in a zig-zagging fashion between the start point and the end at 50N 42W (see accompanying map); the end point may be extended northwards based on SST imagery, in order to ensure that some sampling is achieved north of the Gulf Stream. As time permits, some limited sampling in continental shelf waters off Nova Scotia may also be conducted during the return trip to Woods Hole. The science party will be divided into ‘biology’ (7 members) and ‘chemistry’ (5 members) teams, for a total of 14 participants who will conduct 24-hour operations.

Surveying along the study transect will involve a combination of activities:

1. Underway data will be collected continuously along-track at a survey speed of 8 knots using a multi-frequency acoustic system with hull-mounted transducers; underway measurements will also be conducted using a Multi-parameter Inorganic Carbon Analyzer (MICA). A seabird observer will survey bird abundance during daylight hours.

2. “Regular” stations will be conducted nominally every 1/2 degree in latitude along the transect, involving casts to 1000m with a CTD-VPR package (including bottle samples of seawater) and profiles with the broadband acoustic system to 500m. The exact location of the stations may be adjusted based on real-time examination of data, or time and/or other constraints. Water samples will be processed by chemistry team personnel between stations.

3. “Day/night” stations will be selected from the regular 1/2 degree stations based on real-time examination of the underway acoustic data for evidence of high pteropod abundance. Eight of these day/night stations will be conducted during the cruise, nominally every 2 degrees in latitude along the transect. Day and night MOCNESS net tows and CTD-VPR casts will be made to 1000m. Between these day and night casts/tows, a CTD cast will be made to 3000m. As feasible, small-scale acoustic surveys in the vicinity of the stations will also be performed. Between day/night stations, biology team personnel will process net samples and conduct physiological studies of live sampled animals.

Additional Info

Stations:

Supporting documentation:

Shipboard Equipment

Shipboard Communication

CTD/Water Sampling

Critical CTD Sensors

Hydrographic Analysis Equipment

MET Sensors

Sample Storage

Navigation

Navigation

Winches

Wire use and application

Standard Oceanographic Cables

Checklist

Checklist