Abstract
Abstract. Benthic foraminifera have proven to be suitable for environmental monitoring because of their high levels of adaptation, small size and high abundance in Recent sediments and the fossil record. Foraminifera are scarcely used in monitoring studies because a standardization of methods has not been achieved to date. When particular methods were introduced and why they were applied is often hidden in the literature. This paper reviews the development of field and laboratory methods, their constraints and consequences for faunal and data analyses. Multiple and box corers and some grab samplers retrieve reliable surface sediment samples provided the bow wave is minimized as the sampler approaches the sea floor. Most disturbances are created during handling of the unit on deck and subsampling. Ethanol for preservation, rose Bengal as vital stain and a mesh size of 63 µm to wash foraminiferal samples are used extensively. Faunal analyses of a larger size fraction are occasionally necessary. The fractions >125 µm and >150 µm are often preferentially chosen even though this may artificially reduce specimen numbers and faunal diversity. Generally, a much lower level of common practice prevails in sample preparation and faunal analyses than in sampling or laboratory procedures. Increasing preference has been given to quantitative methods and the acquisition of independently revisable census data during recent decades.
Highlights
IntroductIon Marginal marine ecosystems today are seriously affected by global warming (e.g. Stachowicz et al, 2002; Smith, 2010), the first signs of ensuing ocean acidification (e.g. Cigliano et al, 2010; Thomsen et al, 2010; Haynert et al, 2011), the tremendous growth of mega-cities and the accompanying rise of industrial production in developing countries
The dead assemblages may significantly differ from the living fauna in abundance and species composition due to different production rates of individual species, taphonomic loss of those tests, which are more susceptible to degradation and dissolution, and due to re-deposition (e.g. Murray, 1982)
Apart from taxonomic inconsistencies, these and other approaches are largely hampered by the fact that most of the data from the considered studies were created by using different field and laboratory methods (e.g. Schönfeld, 2006, p. 357)
Summary
JOACHiM SCHöNFELD Helmholtz-Centre for Ocean Research Kiel (GEOMAR), Wischhofstrasse 1–3, D-24148 Kiel, Germany. 1. Sampling devices and preparation utensils used in Recent benthic foraminiferals studies: (a) Van Veen grab (width of jaws in open position is 17 cm); (b) Reineck box corer (width of frame is 100 cm); (c) multicorer at sea on sample recovery (photo: Thorsten Garlichs, Kiel; height of device is 415 cm); (d) microsplitter and Plummer cell slide (length of slide is 7.5 cm). Off southern Portugal, the living benthic foraminiferal assemblage from a core-top sample retrieved with a small gravity corer and plastic core catcher corresponded to a level of 1–3 cm below sediment surface (Schönfeld, 1997; 2001). In high-energy environments, foraminifera often prefer to live attached to stable objects, or they are very rare because of the frequent sediment re-deposition (Schönfeld, 2002a, b) These patterns may be revealed by grab sampling only. Subsampling of box core surfaces for foraminiferal studies is performed in similar ways as hand held sampling on tidal flats.
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