Brittle Stars--Santa Barbara Channel, California

Title: Brittle Stars--Santa Barbara Channel, California
Abstract:: This part of DS 781 presents data for the map showing the predicted distribution of brittle stars in the Santa Barbara Channel, California, region. The raster data file is included in "BrittleStars_SantaBarbaraChannel.zip," which is accessible from <https://pubs.usgs.gov/ds/781/SantaBarbaraChannel/data_catalog_SantaBarbaraChannel.html>. This map showing the predicted distribution of brittle stars in the Santa Barbara Channel is published in Scientific Investigations Map 3225, "California State Waters Map Series--Hueneme Canyon and Vicinity, California" (see sheet 12). In addition, this predicted distribution map will be published in four future California State Waters Map Series SIMs of the region (namely, the Offshore of Ventura, Offshore of Santa Barbara, Offshore of Coal Oil Point, and Offshore of Refugio Beach map areas) [note that, at the time of this writing, one of the other four SIMs has been published: the Offshore of Ventura map area (SIM 3254)].
Presence-absence data of benthic macro-invertebrates and associated habitat (that is, sediment type and depth) were collected using a towed camera sled in selected areas along the coast off southern California during a ground-truth observation cruise conducted by the U.S. Geological Survey and NOAA National Marine Fisheries Service for the California Seafloor Mapping Program. Benthic community structure was determined from 35 video towed-camera transects within California's State Waters 3-nautical-mile limit in the Santa Barbara Channel. These transects produced a total of 923 10-second observations from the Offshore of Refugio Beach map area (34.5 degrees N., 120.1 degrees W.) to the Hueneme Canyon and vicinity map area (34.1 degrees N., 119.2 degrees W.). Presence-absence data were collected for 29 benthic, structure-forming nonmobile taxa. Using this information, generalized linear models (GLMs) were developed to predict the probability of occurrence of five commonly observed taxa (cup corals, hydroids, short and tall sea pens, and brittle stars in the sediment) in five map areas within the Santa Barbara Channel (SBC). A sixth map area (Offshore of Carpinteria) was not modeled owing to insufficient data.
The analysis demonstrates that the community structure for the five map areas can be divided into three statistically distinct groups: (1) the Hueneme Canyon and vicinity and the Offshore of Ventura map areas; (2) the Offshore of Santa Barbara and the Offshore of Coal Oil Point map areas; and (3) the Offshore of Refugio Beach map area. These three distinct groups are the main reason that the probability for each taxa can be so dramatically different within one predictive-distribution map area. The five most frequently observed benthic macro-invertebrate taxa were selected for these predictive-distribution grids. Presence-absence data for each selected invertebrate were fit to specific generalized linear models using geographic location, depth, and seafloor character as covariates. Data for the covariates were informed by the data presented in sheet 2 (shaded-relief bathymetry), sheet 5 (seafloor-character map), and sheet 6 (ground-truth studies) of the five SIM publications of the Santa Barbara Channel region that are part of the California State Waters Map Series.
Observations based on depth were limited by the capability of the towed camera sled; as a result, no predictions were made below depths of 150 m (in other words, on the continental slope or in Hueneme Canyon). Cup corals and hydroids had high predicted probabilities of occurrence in areas of hard substrata, whereas short and tall sea pens were predicted to occur in parts of the SBC that had unconsolidated and mixed sediment. Our model predicted that brittle stars would occur throughout the entire SBC on various bottom types.
Supplemental_Information:: Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
Although this Federal Geographic Data Committee-compliant metadata file is intended to document the data set in nonproprietary form, as well as in ArcInfo format, this metadata file may include some ArcInfo-specific terminology.

Range of values
Minimum:	2.22045e-016
Maximum:	.705603

Range of values

Minimum:

2.22045e-016

Maximum:

.705603

Taxa Model Formulas for GLM: Brittle Star taxa~Depth+I(Depth^2)+ Class+Block+Depth:Block, # Depth+ Depth^2+Class+Block+Depth:Block tryCatch(taxa33.glm <- glm(taxa~Depth+I(Depth^2)+ Class+Block+Depth:Block, family=binomial(link="logit"), data=taxa.df), warning = function(x) { output.df[33,"flag"] <<- 1 }, finally = taxa33.glm <- glm(taxa~Depth+I(Depth^2)+ Class+Block+Depth:Block, family=binomial(link="logit"), data=taxa.df) ) summary(taxa33.glm) MODEL SUMMARY: ============== Call: glm(formula = brit_in ~ Depth + I(Depth^2) + factor(Class) + factor(Block) + Depth:factor(Block), family = binomial(link="logit"), data = na.omit(d)) Deviance Residuals: Min 1Q Median 3Q Max -1.5551 -0.6983 -0.4912 -0.1107 2.7408 Coefficients: Estimate Std. Error z value Pr(>|z|) (Intercept) -1.6441219 0.6640992 -2.476 0.01330 * Depth 0.1144813 0.0234621 4.879 1.06e-06 *** I(Depth^2) -0.0013578 0.0002068 -6.567 5.13e-11 *** factor(Class)2 -0.9254904 0.3303862 -2.801 0.00509 ** factor(Class)3 -0.8756778 0.5539213 -1.581 0.11391 factor(Block)2 -1.5455724 0.5615242 -2.752 0.00591 ** factor(Block)3 -4.4970380 0.7311817 -6.150 7.73e-10 *** Depth:factor(Block)2 0.0061871 0.0092539 0.669 0.50376 Depth:factor(Block)3 0.0807144 0.0147237 5.482 4.21e-08 *** --- Signif. codes: 0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1 (Dispersion parameter for binomial family taken to be 1) Null deviance: 1009.10 on 922 degrees of freedom Residual deviance: 841.58 on 914 degrees of freedom AIC: 859.58 Number of Fisher Scoring iterations: 5 Analysis of Deviance Table Model: binomial, link: logit Response: brit_in Terms added sequentially (first to last) Df Deviance Resid. Df Resid. Dev NULL 922 1009.10 Depth 1 2.14 921 1006.96 I(Depth^2) 1 85.43 920 921.53 factor(Class) 2 8.31 918 913.22 factor(Block) 2 43.91 916 869.30 Depth:factor(Block) 2 27.72 914 841.58 resampled to 10 meters

Brittle Stars--Santa Barbara Channel, California

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