Karl Norling

Response of single benthic metrics and multi-metric methods to anthropogenic pressure gradients, in five distinct European coastal and transitional ecosystems

In recent times many benthic indices have been proposed to assess the ecological quality of marine waters worldwide. In this study we compared single metrics and multi-metric methods to assess coastal and transitional benthic status along human pressure gradients in five distinct environments across Europe: Varna bay and lake (Bulgaria), Lesina lagoon (Italy), Mondego estuary (Portugal), Basque coast (Spain) and Oslofjord (Norway). Hence, 13 single metrics (abundance, number of taxa, and several diversity and sensitivity indices) and eight of the most common indices used within the European Water Framework Directive (WFD) for benthic assessment were selected: index of size spectra (ISS), Benthic assessment tool (BAT), Norwegian quality index (NQI), Multivariate AMBI (M-AMBI), Benthic quality index (BQI), (Benthic ecosystem quality index (BEQI), Benthic index based on taxonomic sufficiency (BITS), and infaunal quality index (IQI). Within each system, sampling sites were ordered in an increasing pressure gradient according to a preliminary classification based on professional judgement. The different indices are largely consistent in their response to pressure gradient, except in some particular cases (i.e. BITS, in all cases, or ISS when a low number of individuals is present). Inconsistencies between indicator responses were most pronounced in transitional waters (i.e. IQI, BEQI), highlighting the difficulties of the generic application of indicators to all marine, estuarine and lagoonal environments. However, some of the single (i.e. ecological groups approach, diversity, richness) and multi-metric methods (i.e. BAT, M-AMBI, NQI) were able to detect such gradients both in transitional and coastal environments, being these multi-metric methods more consistent in the detection than single indices. This study highlights the importance of survey design and good reference conditions for some indicators. The agreement observed between different methodologies and their ability to detect quality trends across distinct environments constitutes a promising result for the implementation of the WFDs monitoring plans. Moreover, these results have management implications, regarding the dangers of misclassification, uncertainty in the assessment, use of conflicting indices, and testing and validation of indices.

Biotic and Human Vulnerability to Projected Changes in Ocean Biogeochemistry over the 21st Century

Mora and colleagues show that ongoing greenhouse gas emissions are likely to have a considerable effect on several biogeochemical properties of the worlds oceans, with potentially serious consequences for biodiversity and human welfare.

Effects of the invasive red king crab (Paralithodes camtschaticus) on soft-bottom fauna in Varangerfjorden, northern Norway

The red king crab (Paralithodes camtschaticus) was introduced from the northern Pacific to the Russian Murman coast during the 1960s and 1970s. Over the subsequent decades, the crab has become established in northern Norwegian waters, where it continues spreading westward. The crab is an active predator on benthic fauna, especially feeding in deep soft-bottom environments. The present studies, carried out in the Varanger area close to the Russian border in 2007-2009, indicate that soft-bottom epifauna and infauna have become markedly reduced in crab-invaded areas. For infauna, quantitative data from 1994 were used as a basis to compare faunal composition before and after the crab became abundant in the area. It appeared that echinoderms, non-moving burrowing and tube-dwelling polychaetes, and most bivalves were reduced, whereas some small-sized polychaetes and small bivalves had increased. In situ sediment profile imagery (SPI) was used to examine sediment structure and biogenic activity. At several locations, the sediment habitat quality was degraded due to hypoxic conditions and low biological activity below surface layers. It is suggested that the crab has removed organisms performing important functions such as bio-irrigation and sediment reworking. Hence, it appears that the crab may reduce the functional diversity of the resident species assemblages, which may have overall implications for ecosystem function, production and responses to other environmental stressors.

Rapid macrofaunal colonization of water-based drill cuttings on different sediments

A field experiment was conducted to investigate how water-based drill cuttings and sediment type influence colonization of soft bottom communities. Bottom frames with trays containing defaunated sediments were placed at the seabed for 6 months to study colonization of macrofauna. Two different sediments (coarse and fine) were used, and 6 or 24 mm layer of water-based drill cuttings were added on top of these sediments. Some of the sediments were controls with no additions. In the end of the experiment, the oxygen availability in sediment porewater and macrofaunal abundance were reduced in treatments with 24 mm drill cuttings compared to controls. Tube-building annelids were particularly sensitive to drill cuttings. However, these responses were only minor, and notably, the drill cuttings initiated a weaker faunal response than sediment type and site of the bottom frame. Sediments capped with water-based drill cuttings thus showed a rapid colonization of macrofaunal communities.