Dataset: Pre-experiment Urchin Barren Characterization

Name: Pre-experiment Urchin Barren Characterization
Published: 2024-11-01
Keywords: sea star wasting disease, kelp restoration, oceans

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Spatial Extent: N:57.036 E:-135.255 S:57.033 W:-135.28

Sitka Sound, Alaska, USA (57.033762 N, 135.264282 W) depth 6-9m

Temporal Extent: 2023-02-11 - 2023-02-20

Project:

CAREER: Energy fluxes and community stability in a dynamic, high-latitude kelp ecosystem (High latitude kelp dynamics)

Principal Investigator:

Kristy J. Kroeker (University of California-Santa Cruz, UCSC)

Co-Principal Investigator:

Aaron W.E. Galloway (University of Oregon)

Sarah Gravem (Oregon State University, OSU)

Peter T. Raimondi (University of California-Santa Cruz, UCSC)

Student:

Rose S. Campbell (University of California-Santa Cruz, UCSC)

Nathan Hunter (University of California-Santa Cruz, UCSC)

Raphael T. Mancuso (University of California-Santa Cruz, UCSC)

Contact:

Rose S. Campbell (University of California-San Diego, UCSD)

BCO-DMO Data Manager:

Sawyer Newman (Woods Hole Oceanographic Institution, WHOI BCO-DMO)

Version:

Version Date:

2024-11-01

Restricted:

Validated:

Current State:

Preliminary and in progress

Urchin barren characterization before installment of experimental Pycnopodia cages in Sitka Sound, February 2023

Abstract:

Before experimental manipulation with caged Pycnopodia helianthoides presence, we characterized ambient density, gonad index, and size distributions of urchin communities ( Strongylocentrotus droebachiensis and Mesocentrotus franciscanus) in three replicate urchin barrens in Sitka Sound, AK (57°2'1"N 135°15'51"W) from February 11-20, 2023. Via SCUBA we conducted swath surveys where grazers were identified, counted, measured (test diameter), and randomly collected for gonad dissections. These surveys serve as a baseline to describe these sites as true barrens and to compare experimental results to.

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Methods & Sampling

Surveys

Three urchin barren sites, Ellsworth Cut (57.036, -135.280), Harris Island (57.033, -135.277), and Whale Park (57.033, -135.255), were identified as potential sites for Pycnopodia experiments because they all had transitioned in the last several years from kelp-dominated habitats to barren. Sites were qualitatively similar in rugosity (low rugosity), substrate (bedrock, with some boulder and cobbles), and depth (6-9m). In order to better characterize the shifting state of these subtidal environments before experimental manipulation, we surveyed the density and size structure of dominant grazers (H. kamtschatkana, M. franciscanus and S. droebachiensis) at each site using a swath approach on SCUBA (2 x 30m at Ellsworth Cut and Harris Island, and 2 x 15m at Whale Point). Urchin test diameters and longest abalone shell lengths were measured with calipers.

Gonad Indices

We also compared the gonad indices of randomly collected red sea urchins (M. franciscanus) at our three sites to an intact kelp forest reference site (Magic Island; 57.098, -135.401) about ~12 km away from the nearest experimental site. We measured the gonad index of M. franciscanus individuals from each site (N = 9-11) as: [wet mass of gonadal tissue/ total mass of the organism]*100.

Analysis

Mean and standard deviation of density and size were calculated for each species at all three barren sites with each 10m2 block of the swath surveys acting as a replicate. H. kamtchatkana was dropped from analysis for low replication. Two sample independent t-tests were used to compare means and variances between urchin species groups for density and size across sites. Gonad index was calculated and averaged for each barren site and the singular kelp forest site. T-tests were similarly used to compare average gonad content in barren sites versus the kelp forest site.

BCO-DMO Processing

- Added a column "ISO_Datetime" from the separate date and time columns (the original columns have been retained within the data file)

More Information about this dataset

Funding Sources

Funding Source	Award Number
NSF Division of Ocean Sciences	OCE-1752600

Deployments

None available yet

Instruments

None available yet

Parameters

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

Supplied Name	Supplied description	Supplied Units	Standard Name
Lat	Latitude	decimal degrees	lat
Long	Longitude	decimal degrees	lon
Site	Urchin barren site name.	unitless	site
ISO_DateTime	Date time in UTC. Format: %Y-%m-%dT%H:%M:%S	unitless	ISO_DateTime_UTC
Date	YYYY-MM-DD, AKST (Alaska Standard Time), UTC-9. Format: %Y-%m-%d	unitless	date
Time	HH:MM, AKST (Alaska Standard Time), UTC-9.	unitless	time_local
Diver	Diver identity.	unitless	person
Meter_marks	5mx2m block along 30m long transect that diver sampled.	unitless	exp_id
Species	Grazer species (HALIKAM=Haliotis kamtschatkana, STRODRO= Strongylocentrotus droebachiensis, STROFRAN=Mesocentrotus franciscanus).	unitless	species
Scientific_Name	Scientific name of represented species in this data file.	unitless	species
Count	Count of corresponding species in that block of swath.	individual	count
Area_m2	Area sample for respective count and size data, if <10 diver subsampled due to high urchin density.	meters squared (m2)	area
Density_m2	Count of grazer species divided by sampled area.	meters squared (m-2)	density
notes	Field notes.	unitless	comment

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Dataset: Pre-experiment Urchin Barren Characterization