Variability in northwards extension of warm water copepods in the NE Pacific

The Continuous Plankton Recorder has been deployed in the NE Pacific on two intersecting transects since 2000. Many deployments included a temperature sensor providing in situ temperature data to supplement the species abundance data for 1300 samples. Twenty-nine copepod taxa were sufficiently abundant to examine their temperature-related distributions. Groups of warm- and cold-water species were identified, with overlapping distributions between 48 and 588N. Recent fluctuations in ocean climate, from the warmest year on record in 2005 to one of the coldest in decades in 2008, provided ideal conditions to observe temperature-related interannual variability. The abundance and northwards extension of warm water species were significantly positively correlated with mean annual temperature and the Pacific Decadal Oscillation. The cold water species showed no correlations with temperature/Pacific Decadal Oscillation (PDO) within the study region; however, if the 4 years of sampling that extended south to 398N were examined separately, there was a strong relationship between temperature/PDO and the southern extent of subarctic copepods. Under warm ocean conditions, the range overlap of the two groups will increase as warm water species extend northwards, causing an increase in copepod diversity. Since warm water species are generally smaller and nutritionally poorer, this has implications for higher trophic levels

Warm-water decapods and the trophic amplification of climate in the North Sea

A long-term time series of plankton and benthic records in the North Sea indicates an increase in decapods and a decline in their prey species that include bivalves and flatfish recruits. Here, we show that in the southern North Sea the proportion of decapods to bivalves doubled following a temperature-driven, abrupt ecosystem shift during the 1980s. Analysis of decapod larvae in the plankton reveals a greater presence and spatial extent of warm-water species where the increase in decapods is greatest. These changes paralleled the arrival of new species such as the warm-water swimming crab Polybius henslowii now found in the southern North Sea. We suggest that climate-induced changes among North Sea decapods have played an important role in the trophic amplification of a climate signal and in the development of the new North Sea dynamic regime.

Bacterial symbiosis in Syssitomya pourtalesiana Oliver, 2012 (Galeommatoidea: Montacutidae), a bivalve commensal with the deep-sea echinoid Pourtalesia.

For the first time, bacterial symbiosis is recognized in the bivalve family Montacutidae of the superfamily Galeommatoidea. The ctenidial filaments of Syssitomya pourtalesiana Oliver, 2012 are extended abfrontally and a dense layer of bacteriocyte cells cover the entire surface behind a narrow ciliated frontal zone. The bacteria are extracellular and held within a matrix of epithelial extensions and microvilli. There is no cuticular layer (glycocalyx) covering the bacteria as in many thyasirid symbioses. The bacteriocytes hold more than one morphotype of bacteria, but bacilli, 1–3 μm in length, dominate. Scanning electron microscopy observations show a surface mat of filamentous bacteria over the extreme abfrontal surfaces. Filter feeding was confirmed by the presence of food particles in the stomach and the bivalve is presumed to be mixotrophic. Syssitomya is commensal and lives attached to the anal spines of the deep-sea echinoid Pourtalesia. In this position, echinoid feeding currents and echinoid faecal material may supply the bacteria with a variety of nutrient materials including dissolved organic matter.