Long-term changes in the macrozoobenthos around the rocky island of Helgoland (German Bight, North Sea)

Abstract

The paper briefly summarizes what is known about long-term changes (facts, causes, consequences) in the macrozoobenthos of intertidal and subtidal hardbottom communities around the island of Helgoland (German Bight, North Sea). There is increasing observational evidence that these communities (spectrum and abundances of species) are changing on a long-term temporal scale. The reasons are diverse and mainly anthropogenic. A shift in North Sea climate towards more oceanic conditions may be among the most important factors driving the recent changes in species spectrum. Many of the species which have been recorded as new to the Helgoland area during the past decade are southern (oceanic) species which may be considered as indicators of a warming trend.

On the occurrence of Diogenes pugilator in the German Bight (Crustacea: Decapoda Diogenidae)

“…Such spreads have been recorded for a number of animal groups (Franke and Gutow 2004;Beermann and Franke 2011 for Amphipoda;Franke et al 1999 for an isopod; Beare et al 2004 for fish). Long-term studies and observations are necessary, though missing in many cases, in order to get an idea on the dynamics of such invasions.…”

“…The present study summarises the data of the specimens collected in the period 2005-2013 from and off the Eastern Frisian Island of Wangerooge and presents morphometric details. Before this, it had already been found around the offshore island of Helgoland (Franke and Gutow 2004), from off Borkum Island (Pätzold and Stamm 2012), and from an unspecified locality at the East Frisian coast (Gehrmann 2009), later specified as off Neuharlinger Siel (Gehrmann 2011), and onshore at the Islands Baltrum and Norderney (Gehrmann 2011), Wangerooge as well as in the Jade Bay (both Türkay 2008).…”

Ecological long-term research at Helgoland (German Bight, North Sea): retrospect and prospect?an introduction

“…Most of them are oceanic or warm water species which, as potential indicators of a warming trend, seem to be about to extent their range from Atlantic waters into the North Sea (e.g. Greve et al 1996;Franke et al 1999;Franke and Gutow 2004). On the other hand, the continued existence of populations which are at their southern distributional limit at Helgoland seems to be threatened.…”

“…On the other hand, the continued existence of populations which are at their southern distributional limit at Helgoland seems to be threatened. Some species of macroalgae and invertebrates have been introduced intentionally or unintentionally by man and have successfully established themselves as permanent members of the local ecosystem (Bartsch and Tittley 2004;Franke and Gutow 2004). The most recent example is the Pacific oyster (Crassostrea gigas), which was first recorded at Helgoland in 2003.…”

“…58,no. 4) presents a series of seven publications summarizing long-term studies at Helgoland on bacteria (Gerdts et al 2004), phytoplankton (Hoppenrath 2004;Wiltshire and Du¨rselen 2004;Wiltshire and Manley 2004), zooplankton (Greve et al 2004), macroalgae communities (Bartsch and Tittley 2004) and the macro-zoobenthos (Franke and Gutow 2004). Additional papers on related topics will appear in irregular succession.…”