Population dynamics of the burrowing ghost shrimpCallianassa filholion an intertidal sandflat in New Zealand (Decapoda: Thalassinidea)

Estimating Long-term Trends in Populations of Two Ecosystem Engineering Burrowing Shrimps in Pacific Northwest (USA) Estuaries

Temporal variation in the density and distribution of the burrowing shrimps, Neotrypaea californiensis and Upogebia pugettensis, were compared in two estuaries along the West coast of the United States (USA) where they are recognized as important ecosystem engineers. Since these shrimp construct deep burrows in the sediment, we quantified the relationship between burrow openings and shrimp density (1.5 and 1.7 burrow openings per shrimp for N. californiensis and U. pugettensis respectively) to permit population abundance estimates to be made over broad landscape scales. Neotrypaea californiensis populations estimated from burrow counts collected using a gridded survey design across representative tide flats declined by 25% between 2008-2010 in Yaquina Bay, Oregon and by 67% in Willapa Bay, Washington from 2006-2011, but increased again in Willapa Bay by 2014. Upogebia pugettensis had mostly disappeared from Willapa Bay by 2006 and declines were observed in Yaquina Bay, but the magnitude and long-term trajectory of U. pugettensis in this estuary was less clear. These species population fluctuations mirrored those observed in density collected at discrete sampling locations over the same period, equate to large changes in secondary production, and have likely resulted in substantial changes to estuarine habitat and food webs.

Estimating the effect of burrowing shrimp on deep-sea sediment community oxygen consumption

Sediment community oxygen consumption (SCOC) is a proxy for organic matter processing and thus provides a useful proxy of benthic ecosystem function. Oxygen uptake in deep-sea sediments is mainly driven by bacteria, and the direct contribution of benthic macro- and mega-infauna respiration is thought to be relatively modest. However, the main contribution of infaunal organisms to benthic respiration, particularly large burrowing organisms, is likely to be indirect and mainly driven by processes such as feeding and bioturbation that stimulate bacterial metabolism and promote the chemical oxidation of reduced solutes. Here, we estimate the direct and indirect contributions of burrowing shrimp (Eucalastacus cf. torbeni) to sediment community oxygen consumption based on incubations of sediment cores from 490 m depth on the continental slope of New Zealand. Results indicate that the presence of one shrimp in the sediment is responsible for an oxygen uptake rate of about 40 µmol d^-1, only 1% of which is estimated to be due to shrimp respiration. We estimate that the presence of ten burrowing shrimp m^-2 of seabed would lead to an oxygen uptake comparable to current estimates of macro-infaunal community respiration on Chatham Rise based on allometric equations, and would increase total sediment community oxygen uptake by 14% compared to sediment without shrimp. Our findings suggest that oxygen consumption mediated by burrowing shrimp may be substantial in continental slope ecosystems.

Ghost shrimps (Decapoda: Axiidea: Callianassidae) as producers of an Upper Miocene trace fossil association from sublittoral deposits of Lake Pannon (Vienna Basin, Slovakia)

Numerous trace fossils are described from the Late Miocene sediments of the Bzenec Formation exposed at the Gbely section (the Vienna Basin, Slovakia). During deposition of the sediments the area was part of the large, long-lived brackish to freshwater Lake Pannon. Most of the trace fossils are attributed herein to Egbellichnus jordidegiberti igen et ispec. nov. and are interpreted as burrows produced by decapod crustaceans, specifically by a ghost shrimp of the family Callianassidae. This interpretation is based on two independent lines of evidence: environmental requirements of large bioturbators and the burrow morphology itself. The new ichnotaxon is distinguished from other related ichnotaxa by a combination of typically inclined (roughly at an angle of 45°) cylindrical burrows, absence of lining, and tunnels making loops or bends at approximately right angles. The burrow systems at Gbely document the survival of ghost shrimp long after the closure of all seaways and the origin of Lake Pannon. As today, no ghost shrimp are known from long-lived brackish lakes. Egbellichnus from Gbely is the only, although indirect, record of ghost shrimp from a brackish lake environment reported so far.