MEPS 522:79-95 (2015)  -  DOI:

Mapping and modeling eelgrass Zostera marina distribution in the western Baltic Sea

Philipp R. Schubert1,*, Wolfgang Hukriede1, Rolf Karez2, Thorsten B. H. Reusch1

1Evolutionary Ecology of Marine Fishes, GEOMAR Helmholtz Center for Ocean Research Kiel, Düsternbrooker Weg 20,
24105 Kiel, Germany
2State Agency for Agriculture, Environment and Rural Areas Schleswig-Holstein (LLUR), Hamburger Chaussee 25,
24220 Flintbek, Germany
*Corresponding author:

ABSTRACT: In the northern hemisphere, eelgrass Zostera marina L. is the most important and widespread seagrass species. Despite its ecological importance, baseline data on eelgrass distribution and abundance are mostly absent, particularly in subtidal areas with relatively turbid waters. Here, we report a combined approach of vegetation mapping in the Baltic Sea coupled to a species distribution model (SDM). Eelgrass cover was mapped continuously in the summers of 2010 and 2011 with an underwater towed camera along ~400 km of seafloor. Eelgrass populated 80% of the study region and occurred at water depths between 0.6 and 7.6 m at sheltered to moderately exposed coasts. Mean patch length was 128.6 m but was higher at sheltered locations, with a maximum of >2000 m. The video observations (n = 7824) were used as empiric input to the SDMs. Using generalized additive models, 3 predictor variables (depth, wave exposure, and slope), which were selected based on Akaike’s information criterion, were sufficient to predict eelgrass presence/absence. Along with a very good overall discriminative ability (area under the receiver-operating characteristic curve ROC/AUC = 0.82), depth (as a proxy for light), wave exposure, and slope contributed 66, 29, and 5%, respectively, to the final model. The estimated total areal extent of eelgrass in the study region amounts to 140.5 km2 and comprises about 11.5% of all known Baltic seagrass beds. The present work is, to the best of our knowledge, the largest study undertaken to date on vegetation mapping and the first to assess distribution of eelgrass quantitatively in the western Baltic Sea.

KEY WORDS: Species distribution · GAM · Habitat mapping · Habitat modeling · Depth limit · Patchiness

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Cite this article as: Schubert PR, Hukriede W, Karez R, Reusch TBH (2015) Mapping and modeling eelgrass Zostera marina distribution in the western Baltic Sea. Mar Ecol Prog Ser 522:79-95.

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