Development and validation of a molecular technique for the analysis of archived formalin-preserved phytoplankton samples permits retrospective assessment of Emiliania huxleyi communities

The coccolithophores, particularly the species Emiliania huxleyi (Lohmann) Hay & Mohler, account for the bulk of global calcium carbonate production and as such play a fundamental role in global CO2 cycling and the carbonate chemistry of the oceans. To evaluate the response of this functional group to the effects of climate change, we undertook a feasibility study to determine whether a retrospective approach could be used on archived coccolithophore datasets. We demonstrate for the first time a technique for the extraction of E. huxleyi nucleic acids from archived formalin-fixed samples of the long-term Continuous Plankton Recorder. Molecular analysis of a nine year old formalin-fixed sample reveals the presence of a diverse population of E. huxleyi genotypes within a developing coccolithophore bloom. In addition, E. huxleyi sequences were amplified from a number of formalin-fixed samples, the earliest of which was collected in August 1972. This molecular assay promises the possibility of studying global variations in the distribution and genetic make-up of E. huxleyi communities over extensive periods of time. (c) 2008 Elsevier B.V. All rights reserved.

Effects of formalin preservation on stable carbon and nitrogen isotope signatures in Calanoid copepods: implications for the use of Continuous Plankton Recorder Survey samples in stable isotope analyses

Preserved and archived organic material offers huge potential for the conduct of retrospective and long-term historical ecosystem reconstructions using stable isotope analyses, but because of isotopic exchange with preservatives the obtained values require validation. The Continuous Plankton Recorder (CPR) Survey is the most extensive long-term monitoring program for plankton communities worldwide and has utilised ships of opportunity to collect samples since 1931. To keep the samples intact for subsequent analysis, they are collected and preserved in formalin; however, previous studies have found that this may alter stable carbon and nitrogen isotope ratios in zooplankton. A maximum ~0.9‰ increase of δ15N and a time dependent maximum ~1.0‰ decrease of δ13C were observed when the copepod, Calanus helgolandicus, was experimentally exposed to two formalin preservatives for 12 months. Applying specific correction factors to δ15N and δ13C values for similarly preserved Calanoid species collected by the CPR Survey within 12 months of analysis may be appropriate to enable their use in stable isotope studies. The isotope values of samples stored frozen did not differ significantly from those of controls. Although the impact of formalin preservation was relatively small in this and other studies of marine zooplankton, changes in isotope signatures are not consistent across taxa, especially for δ15N, indicating that species-specific studies may be required. Copyright © 2011 John Wiley & Sons, Ltd.

Maintenance of abyssal benthic foraminifera under high pressure and low temperature: some preliminary results

Abyssal benthic foraminifera have been maintained alive for periods of several weeks under laboratory simulated deep-sea conditions of high pressure and low temperature. In separate experiments, bacterial-sized fluorescent microspheres and three species of microalgae were supplied as food particles. Subsequent light and electron microscopy showed that the algae had been ingested by several foraminiferal species. Furthermore, the fine structure of the foraminiferal cytoplasm was well-preserved which indicates, along with the ingestion of algal food, that they had remained in a viable condition during the incubation. Other observations indicate that abyssal benthic foraminifera ingest naturally occurring photosynthetic cells carried to the deep-sea bed by rapidly sedimenting aggregates. The ability to keep foraminifera originating from depths exceeding 4000 m alive in the laboratory paves the way for the experimental investigation of some important issues in deep-sea biology and palaeoceanography.