A perceived recent increase in global jellyfish abundance has been portrayed as a symptom of degraded oceans. This perception is based primarily on a few case studies and anecdotal evidence, but a formal analysis of global temporal trends in jellyfish populations has been missing. Here, we analyze all available long-term datasets on changes in jellyfish abundance across multiple coastal stations, using linear and logistic mixed models and effect-size analysis to show that there is no robust evidence for a global increase in jellyfish. Although there has been a small linear increase in jellyfish since the 1970s, this trend was unsubstantiated by effect-size analysis that showed no difference in the proportion of increasing vs. decreasing jellyfish populations over all time periods examined. Rather, the strongest nonrandom trend indicated jellyfish populations undergo larger, worldwide oscillations with an approximate 20-y periodicity, including a rising phase during the 1990s that contributed to the perception of a global increase in jellyfish abundance. Sustained monitoring is required over the next decade to elucidate with statistical confidence whether the weak increasing linear trend in jellyfish after 1970 is an actual shift in the baseline or part of an oscillation. Irrespective of the nature of increase, given the potential damage posed by jellyfish blooms to fisheries, tourism, and other human industries, our findings foretell recurrent phases of rise and fall in jellyfish populations that society should be prepared to face.

A newly-constructed antibody-like molecule containing the gp120-binding domain of the receptor for human immunodeficiency virus blocks HIV-1 infection of T cells and monocytes. Its long plasma half-life, other antibody-like properties, and potential to block all HIV isolates, make it a good candidate for therapeutic use.

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We combined 3 different approaches to determine the relative importance of microphytobenthos production as food for intertidal macrobenthic animals: (1) the natural abundance of stable-isotope ratios of carbon and nitrogen, (2) an in situ deliberate tracer addition of 13 C-bicarbonate, which was transferred through the benthic food chain after its incorporation by benthic algae, and (3) a dual labelling experiment in a flume, where pelagic and benthic algae were labelled with 15 N and 13 C, respectively. The results of the 3 approaches confirmed the high importance of microphytobenthos as a food source for (surface) deposit feeders. Despite the clearly demonstrated resuspension of benthic algae at high current velocities, suspension feeders appeared to depend almost exclusively on pelagic algae (and possibly detrital carbon) as a food source. Based on the results of the experiments, we determined an approximate degree of dependence on microphytobenthos for different species of intertidal macrobenthos. The macrobenthic biomass at 5 study locations, when weighted by these coefficients, correlated very well with measured productivity of the microphytobenthos.

miCHael n daWson, maRy betH deCKeR, Claudia e. mills, JennifeR e. PuRCell, alenKa maleJ, HeRmes mianzan, sHin-iCHi uye, stefan GelCiCH, and lauRenCe P. madin During the past several decades, high numbers of gelatinous zooplankton species have been reported in many estuarine and coastal ecosystems. Coupled with media-driven public perception, a paradigm has evolved in which the global ocean ecosystems are thought to be heading toward being dominated by "nuisance" jellyfish. We question this current paradigm by presenting a broad overview of gelatinous zooplankton in a historical context to develop the hypothesis that population changes reflect the human-mediated alteration of global ocean ecosystems. To this end, we synthesize information related to the evolutionary context of contemporary gelatinous zooplankton blooms, the human frame of reference for changes in gelatinous zooplankton populations, and whether sufficient data are available to have established the paradigm. We conclude that the current paradigm in which it is believed that there has been a global increase in gelatinous zooplankton is unsubstantiated, and we develop a strategy for addressing the critical questions about long-term, human-related changes in the sea as they relate to gelatinous zooplankton blooms.

Among marine organisms, gelatinous zooplankton (GZ; cnidarians, ctenophores, and pelagic tunicates) are unique in their energetic efficiency, as the gelatinous body plan allows them to process and assimilate high proportions of oceanic carbon. Upon death, their body shape facilitates rapid sinking through the water column, resulting in carcass depositions on the seafloor ("jelly-falls"). GZ are thought to be important components of the biological pump, but their overall contribution to global carbon fluxes remains unknown. Using a data-driven, three-dimensional, carbon cycle model resolved to a 1°global grid, with a Monte Carlo uncertainty analysis, we estimate that GZ consumed 7.9-13 Pg C y −1 in phytoplankton and zooplankton, resulting in a net production of 3.9-5.8 Pg C y −1 in the upper ocean (top 200 m), with the largest fluxes from pelagic tunicates. Non-predation mortality (carcasses) comprised 25% of GZ production, and combined with the much greater fecal matter flux, total GZ particulate organic carbon (POC) export at 100 m was 1.6-5.2 Pg C y −1 , equivalent to 32-40% of the global POC export. The fast sinking GZ export resulted in a high transfer efficiency (T eff) of 38-62% to 1,000 m and 25-40% to the seafloor. Finally, jelly-falls at depths >50 m are likely unaccounted for in current POC flux estimates and could increase benthic POC flux by 8-35%. The significant magnitude of and distinct sinking properties of GZ fluxes support a critical yet underrecognized role of GZ carcasses and fecal matter to the biological pump and air-sea carbon balance. Plain Language Summary Marine ecosystems play a critical role in the global carbon cycle through food web regulation of air-sea carbon fluxes and the transfer of organic carbon from the upper oceans to the deep sea. The carcasses of gelatinous zooplankton (GZ), which include jellyfish and salps, have been found in mass seafloor depositions ("jelly-falls") in many locations. These jelly-falls are thought to be a fast mechanism for carbon sequestration, yet no global studies on their overall impact have been done. Using a database of GZ observations, we suggest that the inclusion of previously unaccounted for GZ carbon in seafloor carbon deposition could increase current estimates by 8-35%. This previously unconsidered flux represents a substantial amount of carbon sequestered in the deep sea.

Annular flumes were used to quantlfy benthic-pelaqc exchanges in relation to changes in current velocity and sediment biota. Various physical, chemical and biological parameters were determined for 4 sites on the Molenplaat tidal flat in the Westerschelde (The Netherlands) during 2 field campaigns in May-June and August-September 1996. These Pcluded: the mass of sediment eroded, maximum and mean erosion rates, critical erosion velocity (Ucfi,), suspension feeding/biodeposition rate, oxygen and ammonium fluxes, density of macrofauna species, chlorophyll a (chl a), colloidal carbohydrate, and physical properties of the sediment. The study showed marked and statistically significant spatial and temporal differences in the potential for sediment erosion. Sites in the centre of the tidal flat were less erodable than those on the edge. All sites on the tidal flat had a significantly (p < 0.001) lower erosion potential in June (i.e. higher U,,, and lower erosion rates) compared to September.The presence of a well-developed microphytobenthos community in June resulted in a statistically significant relationship between U,,, and chl a/colloidal carbohydrate (r = +0.85, p = 0.01). There was a significant relationship (r = +0.88, p = 0.005) between sediment erodab~lity (mass of sediment eroded and erosion rate) and the density of the clam Macoma balthica, a major bioturbator of the surface sedi m e n t~. Analysis of the data also demonstrated significant relationships between clearance rate and Cerastoderma edule biomass (r = +0.91, p < 0.001), and between sedment chl a/colloidal carbohydrate and C. edule biomass (r = +0.92; p < 0.001), reflecting the influence of suspension feeders on both the water column and the sediment, through their biodeposits. The significant increase in sediment erodability between June and September reflected the shift in the overall balance between the major 'biostabilisers' (microphytobenthos) and 'bio-destabilisers' (bioturbating bivalves). T h s interpretation of field-derived correlations is consistent with previously established relationships and mechanistic understanding derived from controlled flume experiments.

We have studied the consequences of introducing human recombinant transforming growth factor beta 1 (hrTGF-beta 1) into synovial tissue of the rat, to begin to better understand the significance of the fact that biologically active TGF-beta is found in human arthritic synovial effusions. Within 4-6 h after the intra-articular injection of 1 microgram of hrTGF-beta 1 into rat knee joints, extensive recruitment of polymorphonuclear leukocytes (PMNs) was observed. Cytochemistry and high resolution histological techniques were used to quantitate the influx of PMNs, which peaked 6 h post-injection. In a Boyden chamber assay, hrTGF-beta 1 at 1-10 fg/ml elicited a chemotactic response from PMNs greater in magnitude than that evoked by FMLP, establishing that TGF-beta 1 is an effective chemotactic agent for PMNs in vitro as well as in vivo. That PMNs may represent an important source of TGF-beta in inflammatory infiltrates was strongly suggested by a demonstration that stored TGF-beta 1 was secreted during phorbol myristate acetate-stimulated degranulation in vitro. Acid/ethanol extracts of human PMNs assayed by ELISA contained an average of 355 ng of TGF/beta 1 per 10(9) cells potentially available for secretion during degranulation of PMNs. [3H]Thymidine incorporation in vivo and autoradiography of tissue sections revealed that widespread cell proliferation was triggered by TGF-beta 1 injection. Synovial lining cells and cells located deep within the subsynovial connective tissue were identified as sources of at least some of the new cells that contribute to TGF-beta 1-induced hyperplasia. Our results demonstrate that TGF-beta is capable of exerting pathogenic effects on synovial tissue and that PMNs may represent a significant source of the TGF-beta present in synovial effusions.