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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.

Jellyfish form spectacular blooms throughout the world's oceans. Jellyfish body plans are characterised by high water and low carbon contents which enables them to grow much larger than non-gelatinous animals of equivalent carbon content and to deviate from non-gelatinous pelagic animals when incorporated into allometric relationships. Jellyfish have, however, been argued to conform to allometric relationships when carbon content is used as the metric for comparison. Here we test the hypothesis that differences in allometric relationships for several key functional parameters remain for jellyfish even after their body sizes are scaled to their carbon content. Data on carbon and nitrogen contents, rates of respiration, excretion, growth, longevity and swimming velocity of jellyfish and other pelagic animals were assembled. Allometric relationships between each variable and the equivalent spherical diameters of jellyfish and other pelagic animals were compared before and after sizes of jellyfish were standardised for their carbon content. Before standardisation, the slopes of the allometric relationships for respiration, excretion and growth were the same for jellyfish and other pelagic taxa but the intercepts differed. After standardisation, slopes and intercepts for respiration were similar but excretion rates of jellyfish were 10× slower, and growth rates 2× faster than those of other pelagic animals. Longevity of jellyfish was independent of size. The slope of the allometric relationship of swimming velocity of jellyfish differed from that of other pelagic animals but because they are larger jellyfish operate at Reynolds numbers approximately 10× greater than those of other pelagic animals of comparable carbon content. We conclude that low carbon and high water contents alone do not explain the differences in the intercepts or slopes of the allometric relationships of jellyfish and other pelagic animals and that the evolutionary longevity of jellyfish and their propensity to form blooms is facilitated by their unique body plans.

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 he 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.

Jellyfish are usually perceived as harmful to humans and are seen as \"pests\". This negative perception has hindered knowledge regarding their value in terms of ecosystem services. As humans increasingly modify and interact with coastal ecosystems, it is important to evaluate the benefits and costs of jellyfish, given that jellyfish bloom size, frequency, duration, and extent are apparently increasing in some regions of the world. Here we explore those benefits and costs as categorized by regulating, supporting, cultural, and provisioning ecosystem services. A geographical perspective of human vulnerability to jellyfish over four categories of human well-being (health care, food, energy, and freshwater production) is also discussed in the context of thresholds and trade-offs to enable social adaptation. Whereas beneficial services provided by jellyfish likely scale linearly with biomass (perhaps peaking at a saturation point), non-linear thresholds exist for negative impacts to ecosystem services. We suggest that costly adaptive strategies will outpace the beneficial services if jellyfish populations continue to increase in the future.

The 2010 Deepwater Horizon (DWH) oil blowout in the Gulf of Mexico began on April 20, originating in the deep sea 66 km off the Louisiana coast. By early June, DWH oil had spread to coastal Louisiana, Mississippi, Alabama and western Florida. An estimated 2,113 km of shoreline were oiled, making DWH the largest marine oil spill in global history by length of affected shoreline. Additionally, a series of oil spill response measures were deployed, including diversions of Mississippi River discharge to forestall oil coming ashore, and the establishment of large-scale fishery closures, with both affecting coastal resources to varying degrees. Here, we review published studies and describe additional analyses evaluating long-term impacts of DWH on coastal/nearshore biological resources. We assembled time-series data collected by state, federal and academic partners on population abundance and environmental conditions to evaluate species and community change. Our study focused on plankton, invertebrates, fishes and dolphins, and 13 “key species” were selected to conduct semi-quantitative vulnerability-resilience (V-R) analyses. At one extreme, early life stages of Gulf Menhaden ( Brevoortia patronus ) were not affected due to seasonal spawning and larval development preceding the spill. In contrast, demographically independent populations of the common Bottlenose Dolphin, ( Tursiops truncatus ) suffered a variety of severe and ongoing health effects owing to oil exposure. Virtually all of the heavily oiled salt marsh habitat was in Louisiana, with the majority occurring in Barataria Bay. Multispecies trawl survey abundances declined post-DWH throughout eastern coastal Louisiana but remained stable elsewhere. A regime shift in composition of Barataria Bay trawl survey catches occurred during and following the spill, the persistence of which was associated with long-term reductions in average salinity and increases in water clarity. In some cases, fishery closures were associated with measurable but ephemeral increases in abundance of some targeted and bycatch species. Freshwater flooding of marshes was ineffective in preventing coastal oiling and severely affected benthic euryhaline resources including Eastern Oyster ( Crassostrea virginica ) and Marsh Periwinkle ( Littoraria irrorata ). The flooding response measure experiment also indicates the directionality of impacts that further planned water diversions may have on ecological communities of lower Mississippi River basins.

The northern Gulf of Mexico (nGOM) is a highly productive region and supports some of the world’s largest fisheries. Mesozooplankton represent a key linkage in coastal food webs for larval fish, both as food and as competition. While many studies have investigated seasonal patterns of mesozooplankton off the Louisiana coast and in the Mississippi Bight, there is little information about mesozooplankton communities on the Texas shelf. In this study, we investigated environmental drivers of mesozooplankton community variability over space and time. Samples were collected on the Texas shelf near Galveston Bay at seasonal intervals following Hurricane Harvey. Total mesozooplankton abundance were found to be highest in September. Diversity exhibited a hump-shaped pattern over the 6 months sampled, with the highest diversity occurring in October 2017. Taxa richness did not vary over the sampling period. Significant differences in mesozooplankton community structure were found only between September 2017 and March 2018. Community abundance was greatest nearshore, and zooplankton diversity was greatest on the shelf. Community structure was found to be driven by both temperature and salinity. Spatial and temporal patterns of specific larval fish prey are presented.

AIM: Scientific debate regarding the future trends, and subsequent ecological, biogeochemical and societal impacts, of gelatinous zooplankton (GZ) in a changing ocean is hampered by lack of a global baseline and an understanding of the causes of biogeographic patterns. We address this by using a new global database of GZ records to test hypotheses relating to environmental drivers of biogeographic variation in the multidecadal baseline of epipelagic GZ biomass in the world's oceans. LOCATION: Global oceans. METHODS: Over 476,000 global GZ data and metadata items were assembled from a variety of published and unpublished sources. From this, a total of 91,765 quantitative abundance data items from 1934 to 2011 were converted to carbon biomass using published biometric equations and species‐specific average sizes. Total GZ, Cnidaria, Ctenophora and Chordata (Thaliacea) biomass was mapped into 5° grid cells and environmental drivers of geographic variation were tested using spatial linear models. RESULTS: We present JeDI (the Jellyfish Database Initiative), a publically accessible database available at http://jedi.nceas.ucsb.edu. We show that: (1) GZ are present throughout the world's oceans; (2) the global geometric mean and standard deviation of total gelatinous biomass is 0.53 ± 16.16 mg C m⁻³, corresponding to a global biomass of 38.3 Tg C in the mixed layer of the ocean; (3) biomass of all gelatinous phyla is greatest in the subtropical and boreal Northern Hemisphere; and (4) within the North Atlantic, dissolved oxygen, apparent oxygen utilization and sea surface temperature are the principal drivers of biomass distribution. MAIN CONCLUSIONS: JeDI is a unique global dataset of GZ taxa which will provide a benchmark against which future observations can be compared and shifting baselines assessed. The presence of GZ throughout the world's oceans and across the complete global spectrum of environmental variables indicates that evolution has delivered a range of species able to adapt to all available ecological niches.

Variability in northern Gulf of Mexico Chrysaora sp. and Aurelia spp. abundance and distribution over time and in relation to climate forces operating at large and regional scales was analyzed using two multi-decadal data sets derived from trawl data collected during fisheries-independent surveys conducted each summer (1987–2007) and fall (1985–2007). Populations exhibited remarkable increases and decreases in size during the past two decades. During peak years, an estimated mean (± 1 SD) total 4.4 (1.5) billion Chrysaora sp. and 9.6 (0.9) billion Aurelia spp. occurred during summer (May–July) and fall (October–November), respectively. Earlier reported increases in jellyfish abundance have not continued; however, the frequency of Chrysaora sp. in trawls has increased with time. Jellyfish ‘‘hot spots’’ are waters southwest of Mobile Bay, west of the Mississippi River outflow, and near the Louisiana–Texas border. ‘‘Cold spots’’ occurred in waters > 40 m in depth. Annual variations in Chrysaora sp. and Aurelia spp. abundance were temporally coherent, suggesting a common set of environmental drivers. Jellyfish abundance was positively related to the El Niño Southern Oscillation, Atlantic Multi-decadal Oscillation, and Pacific Decadal Oscillation and was negatively related to the Great Plains Lower Level Jet. Jellyfish were also more abundant when regional sea surface temperatures were cooler than average in spring and warmer than average in summer–early fall. Increased jellyfish production occurred during years when the northern Gulf experienced wet and warm winters, dry and cool springs, and wet and warm summers and when the Mississippi River watershed experienced dry winters, wet springs, and wet summers.

Prey availability and predation pressure are thought to be key constraints on larval growth, especially in low-productivity, subtropical environments. Yet, measuring their effects on larval fishes has been challenging, given the dynamic biophysical drivers of plankton distributions and small scales of interactions. We integrated fine-scale net tows (10s of meters) with in situ imaging to explore how predator–prey interactions influence larval fish growth in the Straits of Florida. Otolith-derived recent growth was analyzed for 3 ecologically important fishes: 2 coral reef labrids (Thalassoma bifasciatum and Xyrichtys novacula) and 1 tuna (Katsuwonus pelamis), with differing mean growth rates (labrids 0.25 mm d−1, K. pelamis 0.44 mm d−1) and prey (labrids–copepods; tuna–appendicularians). We used generalized additive models to examine the interactive effect of background density and frequency of elevated (>2 SD above background) prey and predators on recent (last 3 d) larval growth. For all taxa, recent growth increased with prey background density. Recent growth of labrids was also higher when copepod densities were more often elevated (14% of transect >20 ind. m−3) above otherwise low background densities (2 ind. m−3). Predators (chaetognaths and hydromedusae) had a growth-selective effect: stronger selection in transects with high-density predator patches, although the direction of the effect was species-specific. The effect of temperature was taxa-specific: growth increased with temperature for the labrids and peaked at an optimum (28°C) for the rapidly growing tuna. Integration of these fine-scale sampling methods improves our understanding of the variable influence of prey and predators on larval growth and, consequently, larval survival.

Tropical cyclones play an increasingly important role in shaping ecosystems. Understanding and generalizing their responses is challenging because of meteorological variability among storms and its interaction with ecosystems. We present a research framework designed to compare tropical cyclone effects within and across ecosystems that: a) uses a disaggregating approach that measures the responses of individual ecosystem components, b) links the response of ecosystem components at fine temporal scales to meteorology and antecedent conditions, and c) examines responses of ecosystem using a resistance–resilience perspective by quantifying the magnitude of change and recovery time. We demonstrate the utility of the framework using three examples of ecosystem response: gross primary productivity, stream biogeochemical export, and organismal abundances. Finally, we present the case for a network of sentinel sites with consistent monitoring to measure and compare ecosystem responses to cyclones across the United States, which could help improve coastal ecosystem resilience.