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Day 3 – Sunday, April 29
The majority of our sampling during this cruise includes repeat visits to sites that have been monitored for a number of years. It is important to collect data over a number of consecutive time periods in order to examine response trends over time. For our seagrass research, we are observing how seagrass responds to a number of disturbances
- hurricanes
- vessel groundings
- manatee grazing
and how it recovers from each of these disturbance types. For our fish research, we are examining how fish communities inhabiting particular habitats fluctuate over time. All of this information is important from a resource management perspective (see the Data Applications section from the Main Page).
Today the seagrass team sampled an area known as Community Beach. A number of plugs of seagrass were collected from within a heavily disturbed meadow of seagrass where manatees are known to feed in large numbers. Plugs were also taken from outside the disturbed area.
- A plug of seagrass is extracted using a 15cm diameter coring tube which is manually pushed into the sediment, capped, and then pulled out.
- The plugs of seagrass are removed from the core, bagged, and returned to the ship for processing.
- On the ship, each plug is thoroughly rinsed to remove all sediment. The first photograph shows Chief Scientist Jud Kenworthy rinsing seagrass samples on the fantail of the ship.
- The numberof individual seagrass shoots per plug are then counted and the shoots are separated into blade material and root material.
- At this stage the seagrass is frozen for future processing upon return to the lab.
Erika Hansen, photo right, is sorting today's seagrass samples.
This year, the fish team is sampling at randomly selected sites encompassing three different habitat types:
- reef,
- seagrass/algae,
- mangrove
and three depth strata:
- outer,
- mid,
- inner.
Green Algae on sea floor.
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Scientist Kevin Kirsch ready to conduct habitat surveys.
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Some sites are new, and some are revisits from 2006. At each site, a diver conducts fish visual census surveys along a 30m transect line identifying and recording all fish sighted within 1m on either side of the line. A second diver follows behind the first and estimates the percent cover, at 5m intervals, of various habitats falling within a 0.5 x 0.5m square.