Dataset: Seastar and chiton counts - quadrats and swaths

Name: Counts of seastars and chiton in quadrats and swaths, north-central California coast: Andrew Molean State Park to Manchester State Park from 2005-2014 (CHIPS project)
Published: 2014-10-13
Keywords: oceans

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Cite This Dataset

Project:

Ecological & genetic recovery from a massive invertebrate die-off along the central coast of California (CHIPS)

Principal Investigator:

Brian Gaylord (University of California-Davis, UC Davis-BML)

Co-Principal Investigator:

Michael N. Dawson (University of California-Merced, UC Merced)

Richard K. Grosberg (University of California-Davis, UC Davis)

Student:

Laura J. Jurgens (University of California-Davis, UC Davis-BML)

Lauren Schiebelhut (University of California-Merced, UC Merced)

Contact:

Laura J. Jurgens (University of California-Davis, UC Davis-BML)

Lauren Schiebelhut (University of California-Merced, UC Merced)

BCO-DMO Data Manager:

Nancy Copley (Woods Hole Oceanographic Institution, WHOI BCO-DMO)

Version:

2014-10-13

Version Date:

2014-10-13

Restricted:

Yes

Validated:

Yes

Current State:

Final no updates expected

Counts of seastars and chiton in quadrats and swaths, north-central California coast: Andrew Molean State Park to Manchester State Park from 2005-2014 (CHIPS project)

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Description

Twenty accessible rocky intertidal sites were selected to span the ‘kill-zone’ and peripheral locations (see list of sites in Jurgens et al. submitted). Two rocky intertidal areas were sampled per site, usually one on either side of the point of entry onto the beach and separated by approximately 100 m. We used quadrats (1m2 [4 * 0.25 m^2] or 0.0625 m^2) and swaths (2 m wide transects) to estimate juvenile and adult abundance for each target species.

This data set includes counts of Pisaster ochraceus, Cryptochiton stelleri and Leptasterias sp. in quadrats and swaths along the California coast from 37.9 N to 38.9 N.

Access Restriction: Access to these data are restricted until publication of the associated manuscript, which is currently in review at PLOS ONE. [2015-02-05]

Methods & Sampling

Quadrats for C. stelleri, Henricia sp., Leptasterias sp., P. ochraceus:
We exhaustively searched 32-40 one-meter square quadrats per site (i.e. 16-20 per each of 2 areas), recording GPS waypoint, time, percent cover of major habitat types, and abundances and sizes of target species for each quadrat. Quadrat locations were selected by first finding one of the target habitat types - surf grass, low-zone red algae, coralline turf, cobble or boulder field, urchin pools with pits either empty or occupied, or mussel bed - selecting a starting point haphazardly, and then using a random numbers table to choose specific quadrat locations. Some sites had fewer than 32 quadrats or quadrats smaller than one-square meter due to the limited time in which we could work in suitable habitat. For mussel habitat one 0.25 m x 0.25 m quadrat was used. For Jurgens et al. (submitted) we calculated the number of each target species summed across all quadrats surveyed within each of the two areas within sites.

Swaths for C. stelleri, Henricia sp., Leptasterias sp., P. ochraceus:
Timed, GPS-tracked, 2 m wide swath transects were nested within each of the two areas within all sites. From a distance, an approximate starting point and orientation (with landmarks) for the starting transect was selected. The GPS was set to auto-record a trackpoint every 6 seconds. Transects ran from the most shoreward to the most seaward possible suitable habitat at approximately 10 m intervals along shore, particularly targeting the low zone when the tide was the lowest, with as many transects being done as permitted by the tide. The start and end of each transect was GPS waypointed and recorded. All target species were searched for across the 2 m wide swath, with intertidal zones and habitat type recorded. A waypoint was recorded for each individual target species, with any additional species found within a meter being counted and recorded for the same waypoint. When the field of view was clear some swaths were extended to 4 meters wide. For Jurgens et al. (submitted) we calculated the number of each target species summed across all swaths within each of the two areas within sites.

Data Processing Description

To estimate swath length we first summed the Euclidean distances between consecutive GPS trackpoints. Given the GPS had an error of +/- 3 meters we smoothed the GPS tracks by averaging across two trackpoints and then by three. We selected a window size of two with which to estimate our total transect length to adjust for the noise in our swath transects but to minimize oversmoothing. (see example figure below). We identified and removed outlying trackpoints that led to a Euclidean distance >=8 meters (likely due to temporarily poor satellite signal). The distance was then recalculated between the trackpoints immediately preceding and following the removed trackpoint. Total transect search area was calculated by multiplying the total adjusted transect length by swath width. Total transect search time was estimated using field notes and GPS waypoints and trackpoints, removing 6-second intervals where < 0.05 m were traveled (suggesting this was time during which notes were being written or tissues samples were being collected).

Swath figure: Sample GPS tracks for two transects at Iversen Point, Mendocino County. The blue line is the original unsmoothed track. The red line represents a window size of two, averaging latitudes and longitudes across each pair of consecutive trackpoints. The green line represents a window size of 3, averaging across 3 trackpoints.

BCO-DMO Processing Notes:

combined quadrat and swath tables
added conventional header with dataset name, PI name, version date, reference information
added lon column
renamed parameters to BCO-DMO standard
sorted by latitude, high to low, then area, then date
changed format of swath area to integer from 11 decimal places to right
moved date column
added area_type column

More Information about this dataset

Funding Sources

Funding Source	Award Number
NSF Division of Ocean Sciences	OCE-1243970
NSF Division of Ocean Sciences	OCE-1243958

Deployments

Deployment	Synonyms	Start Date	Platform	Investigator
CalifCoast_Gaylord_CHIPS		2005-01-01	shoreside Calif_shore	Brian Gaylord (Principal Investigator)	data info

Instruments

Global Positioning System Receiver

Supplied Name: GPS

Supplied Description:

Instrument Type

Generic Name: Global Positioning System Receiver

Acronym: GPS

Community Identifier: http://vocab.nerc.ac.uk/collection/L05/current/POS03/

Generic Description:

The Global Positioning System (GPS) is a U.S. space-based radionavigation system that provides reliable positioning, navigation, and timing services to civilian users on a continuous worldwide basis. The U.S. Air Force develops, maintains, and operates the space and control segments of the NAVSTAR GPS transmitter system. Ships use a variety of receivers (e.g. Trimble and Ashtech) to interpret the GPS signal and determine accurate latitude and longitude.

Parameters

Date and time formats are described in python strftime() syntax.

Supplied Name	Supplied description	Supplied Units	Standard Name
site	survey site name	unitless	site
lat	latitude; north is positive	decimal degrees	lat
lon	longitude; east is positive	decimal degrees	lon
area_type	survey area type: quadrat or swath	unitless	sample_type
area	area of survey	m^2	no_bcodmo_term
date	date of survey	YYYY-MM-DD	date
count_P_ochraceus	Number of Pisaster ochraceus adults found within one quadrat	unitless	count
count_C_stelleri	Number of Cryptochiton stelleri adults found within one quadrat	unitless	count
count_Leptoasterias	Number of Leptasterias adults found within an area of quadrats or swaths as defined in the dataset	unitless	count

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Dataset: Seastar and chiton counts - quadrats and swaths