Influence of temperature on the zoeal development and elemental composition of the cancrid crab, Cancer setosus Molina, 1782 from Pacific South America

Temperature changes during ENSO cause mass mortalities of adult Cancer setosus, but the effects on early life stages are unknown. The influence of temperature on survival, development and biochemical composition was studied in larvae of the hairy crab, C. setosus, from a population off the northern Chilean coast. In rearing experiments conducted at four different temperatures (12, 16, 20, 22 °C), zoeal development was only completed at 16 and 20 °C, after 78 and 36 days, respectively. Instar duration was negatively correlated with temperature. A multiple linear model relating larval body mass (in carbon) to temperature and developmental time suggests that successful larval development is possible within a narrow temperature range only. The biochemical composition, measured as carbon, hydrogen, and nitrogen (C, H, N) content, show in general the typical oscillating changes during the moult cycle of brachyuran crab larvae. However, at high (22 °C) and low (16 °C) temperatures, CHN values show deviations from the typical pattern, indicating threshold temperatures for larval activity and survival. These findings indicate that the larval development of C. setosus is compromised under conditions of El Niño, with temperatures exceeding the upper thermal temperature tolerance threshold of larvae. Effects of El Niño on early life history stages and recruitment rates should be increasingly taken into account in fisheries management strategies.     

Succession of pelagic copepod species in coastal waters off northern Chile: the influence of the 1997–98 El Niño

A 2-year time series (17-d interval) of zooplankton, sampled from June 1996 through January 1998, along with oceanographic data, allowed the study of species abundances and diversity during non-El Niño and El Niño conditions at Mejillones (23° S), northern Chile. A total of 28 species was identified, of which the most abundant were the calanoids Paracalanus parvus, Calanus chilensis, Acartia tonsa, and Centropages brachiatus, the cyclopoid Oithona similis, and the poecilostomatoids Oncaea conifera and Corycaeus typicus. El Niño Southern Oscillation (El Niño) was first detected in the area in May 1997 and persisted until March 1998. We divided the time series into two parts: non-El Niño and El Niño conditions. The number of species significantly increased during El Niño conditions, but total abundance of copepods was greater during non-El Niño conditions. Although some expatriate species appeared during El Niño, such as the harpacticoid Microsetella norvegica and Eucalanus subtenuis, the diversity index of Hulburt was not significantly different between the two periods. Despite the dramatic alteration of oceanographic conditions during the El Niño period, we concluded that the community of pelagic copepods was not subject to drastic changes either in total abundance or in structure.     

Growth and persistence of a recent invader <Emphasis Type="Italic">Carcinus maenas</Emphasis> in estuaries of the northeastern Pacific

During the summer of 1998 a new year class of the invasive European green crab, Carcinus maenas, appeared in Oregon and Washington estuaries as well as in northern California, USA, and on Vancouver Island, Canada. This invader was first discovered in San Francisco Bay almost a decade earlier and by 1995 it had spread to northern California. The coast-wide colonization event we studied in 1998 (El Niño cohort) was correlated with unusually strong north flowing coastal currents from September 1997 to April 1998. Larval transport by ocean currents from established populations to the south appeared to be the mechanism for the colonization. Crabs from the 1998-year class grew faster than counterparts from Maine and Europe, averaging 14 mm in carapace width in June, and 46 mm by September 1998. By the end of their second summer, males ranged from 52 to 80 mm in carapace width, and by fall of 2000 some males attained a carapace width of over 90 mm. The life span for C. maenasit in Oregon, Washington and British Columbia is estimated to be similar as in Europe and Maine: 4–6 years. Even though the initial colonists (98-year class) are dying of senescence, and coastal currents have not been favorable for larval transport from source populations in California, green crabs do persist in Oregon and Washington estuaries. It appears that local reproduction and recruitment in some years is high enough to keep this population from going extinct.     

Microplanktonic respiration off northern Chile during El Nino 1997-1998

Microplanktonic respiration rates were estimated in waters offthe coast of northern Chile (Antofagasta, 23°S) during ElNiño and pre-El Niño conditions. Three cruiseswere conducted during pre-El Niño summer (January/February1997), El Niño winter (July 1997) and El Niñosummer (January 1998). Oxygen consumption was estimated by theWinkler method using a semi-automatic photometric end-pointdetector. The ranges of microplanktonic respiration rates foundwere 0.11–21.15, 0.03–6.25 and 0.06–9.01 µmolO₂ l^–1 day^–1 during pre-El Niño summer, ElNiño winter and El Niño summer, respectively.Significant differences were found between winter and summerrespiration rates (non-integrated and integrated). The meanintegrated respiration (mixed layer) for pre-El Niñosummer, El Niño winter and El Niño summer was95 ± 51 (SD) mmol O₂ m^–2 day^–1, 50 ±23 (SD) mmol O₂ m^–2 day^–1 and 63 ± 32 (SD)mmol O₂ m^–2 day^–1, respectively. The strong seasonalsignal detected in microplanktonic integrated respiration inthe area seems to be characteristic of the pre-El Niño/ElNiño 1997–98 period. The integrated respirationrates found off Antofagasta are similar to reported values forthe upwelling area off Peru despite methodological differences.A positive significant correlation was found between respirationand water temperature (r = 0.76, P     

Estimating scale-dependency in disturbance impacts: El Niños and giant kelp forests in the northeast Pacific

Recent discussions on scaling issues in ecology have emphasized that processes acting at a wide range of spatial and temporal scales influence ecosystems and thus there is no appropriate single scale at which ecological processes should be studied. This may be particularly true for environmental disturbances (e.g. El Niño) that occur over large geographic areas and encompass a wide range of scales relevant to ecosystem function. However, it may be possible to identify the scale(s) at which ecosystems are most strongly impacted by disturbances, and thus provide a measure by which their impacts can be most clearly described, by assessing scale-dependent changes in the patterns of variability in species abundance and distribution. This, in turn, may yield significant insight into the relative importance of the various forcing factors responsible for generating these impacts. The 1997–98 El Niño was one of the strongest El Niños ever recorded. I examined how this event impacted giant kelp populations in the northeast Pacific Ocean at 90 sites ranging from central Baja California, Mexico to central California, USA. These sites spanned the geographic range of giant kelp in the Northeast Pacific and were surveyed just before, immediately following, several months after, more than 1 year after, and nearly 2 years after the El Niño. I used a hierarchical sample design to compare these impacts at five spatial scales spanning six orders of magnitude, from a few meters to more than 1,000 km. Variance Components Analyses revealed that the El Niño shifted control over giant kelp abundance from factors acting at the scale of a few meters (local control) to factors operating over hundreds to thousands of kilometers (regional control). Moreover, El Niño resulted in the near-complete loss of all giant kelp throughout one-half of the species range in the northeast Pacific Ocean. Giant kelp recovery following El Niño was far more complex and variable at multiple spatial scales, presumably driven by numerous factors acting at those scales. Recovery returned local control of giant kelp populations within 6 months in southern California, and within 2 years in Baja California.     

Holocene sand beaches of southern California: ENSO forcing and coastal processes on millennial scales

A proxy record of sand beach accretion for the past 10,000 years has been assembled from radiocarbon dates on the Pismo clam, Tivela stultorum, in archaeological sites along the southern California coast. When this record is compared with numerous climate proxies, it appears that El Niño-Southern Oscillation (ENSO) controls on wave climate and sediment flux have acted upon regional geomorphology at different sea levels to either accrete or erode the Holocene beaches of southern California. Tivela dates from the Santa Maria coast indicate that perennial sand beaches built by 9000 years ago in response to abundant riverine sediment contained by the natural groin at Point Sal, wave sheltering by the massive headland of Point Buchon, and Early Holocene El Niño events. On the western Santa Barbara coast, sand beaches were forming by 7000 years ago in response to high sand fluxes from the Santa Ynez Mountains to the many small littoral catchments, possibly aided by high local rates of uplift. Decline of these sand beach habitats 5000-4000 years ago coincides with increased El Niño-driven wave energy. In accord with slowing in sea-level rise ca. 6000 years ago, sand beaches were most widespread in the period 6000-5000 years ago on Estero Bay, the western Santa Barbara coast, and west of Point Dume. However, Tivela dates first appear 5000 years ago in the Oceanside and Silver Strand littoral cells of the San Diego region. This lag coincides with the Middle Holocene shift to a more variable climate and modern periodicity in El Niño events that increased sediment supply to the southern coast. The ontogeny of the littoral cells provides timelines for modeling coastal evolution with implications for sand beach ecology, prehistoric human coastal adaptations, and coastal planning for future climate change.     

Spatial distribution of small pelagic fish larvae in the Gulf of California and its relation to the El Nino 1997-1998

Sardinops caeruleus larvae were almost absent during the ElNiño 1997–1998, when the sea surface temperature(SST) increased by 4°C. After the event, these larvae appearedin high abundance between 18 and 22°C SST. Engraulis mordaxlarvae were recorded in high abundance during the El Niño(17 and 25°C SST) and afterwards (14 and 22°C). Duringthe event, they tended to concentrate close to Isla Angel deLa Guarda and Isla Tiburón, the coldest zone. The ElNiño conditions affected the spawning of S.caeruleusmore than E.mordax, with the latter more adapted to strong environmentalchanges.     

Reconstructing the range expansion and subsequent invasion of introduced European green crab along the west coast of the United States

The European green crab, Carcinus maenas, was first documented in San Francisco Bay in 1989, and has since spread north along the west coast of North America. The spread of this invasion has not been a smooth expansion, which has raised questions about the underlying causes of variation in recruitment. We modeled larval development and transport along the West Coast by employing an individual-based model that incorporated oceanographic model output of water temperature and ocean currents at fine spatial and temporal scales. The distance that larvae were advected depended primarily on the timing of larval release. However, the effect of seasonal ocean currents varied across latitude and years. Our results imply that the furthest northern transport from California occurs when larvae are released from Humboldt Bay during the fall of an El Niño year, making this a particularly risky time for invasion to Oregon and Washington estuaries. To precisely predict future spread and potential impacts of green crab, we recommend further empirical research to determine the precise timing of larval release and seasonal abundance of green crab larvae from North American west coast populations.     

The impact of El Niño events on populations of mesopelagic hydromedusae

For over 10 years, the midwater ecology group at MBARI has compiled video and accompanying physical data with the ROV Ventana operating in mesopelagic depths of Monterey Bay, CA in order to elucidate patterns in midwater ecology. Two El Niño events have occurred during this time period, in 1991–92 and in 1997–98. The oceanographic metric of spiciness combines temperature and salinity data into one sensitive measurement. Although temperature and salinity measurements alone revealed no clear patterns, clear signals of spiciness were observed that corresponded to water mass intrusions into the deep waters of the bay during the two El Niño events. During these events, some seldom-seen species were observed in high numbers in the midwater, while historically common species became rare. During non-El Niño years, the leptomedusa Mitrocoma cellularia(A. Agassiz, 1865) was common in the surface waters (0–50 m) of Monterey Bay, but it was not abundant at depth, while the trachymedusa Colobonema sericeum Vanhöffen, 1902 was found in relatively high numbers at mesopelagic depths. During the last two El Niño events, M. cellulariawas observed in higher numbers at mesopelagic depths, whereas C. sericeum was scarce. M. cellularia was found in a wider range of temperatures, salinities, and dissolved oxygen values than was C. sericeum. Transport and tolerance hypotheses are proposed to explain differences in the presence and numerical density of the medusae.     

Weather changes associated with hospitalizations for cardiovascular diseases and stroke in California, 1983–1998

Poisson regression models were used to evaluate associations between temperature, precipitation, days of extreme heat, and other weather changes (lagged 7 days), as well as El Niño events, with hospitalizations for acute myocardial infarction, angina pectoris, congestive heart failure, and stroke in three California regions. Temperature changes were defined as a 3 °C decrease in maximum temperature or a 3 °C increase in minimum temperature. Temperature and precipitation were analyzed separately for normal weather periods and El Niño events, and for both weather periods combined. Associations varied by region, age, and gender. In Los Angeles, temperature changes resulted in small changes in hospitalizations. Among San Francisco residents 70+ years of age, temperature changes increased hospitalizations for nearly all outcomes from 6% to 13%. Associations among Sacramento residents were similar to those in San Francisco: among men 70+ years of age, temperature changes increased hospitalizations by 6%–11% for acute myocardial infarction and congestive heart failure, and 10%–18% for stroke. El Niño events were consistently and significantly associated with hospitalizations only in San Francisco and Sacramento, and then only for angina pectoris (increasing hospitalizations during El Niño events). These exploratory analyses merit further confirmation to improve our understanding of how admissions to hospitals for cardiovascular disease and stroke change with changing weather. Such an understanding is useful for developing current public health responses, for evaluating population vulnerability, and for designing future adaptation measures.     

A large impact of tropical biomass burning on CO and CO2 in the upper troposphere

A large interannual variation of biomass burning emissions from Southeast Asia is associated with the ENSO events. During 1997/98 and 1994 El Niño years, uncontrolled wildfires of tropical rainforests and peat lands in Indonesia were enlarged due to a long drought. Enhanced CO injection into the upper troposphere from the intense Indonesian fires was clearly observed in the 8-year measurements from a regular flask sampling over the western Pacific using a JAL airliner between Australia and Japan. This airliner observation also revealed that upper tropospheric CO₂ cycle largely changed during the 1997 El Niño year due partly to the biomass burning emissions. Widespread pollution from the biomass burnings in Southeast Asia was simulated using a CO tracer driven by a 3D global chemical transport model. This simulation indicates that tropical deep convections connected to rapid advection by the subtropical jet play a significant role in dispersing biomass-burning emissions from Southeast Asia on a global scale.     

Mortalities of kelp-forest fishes associated with large oceanic waves off central California, 1982–1983

Synopsis Observations of three incidents of the mass mortality of nearshore fishes are reported; each corresponded to periods of high-amplitude, long-period swells during the 1982–1983 El Niño event along the coast of central California. Members of the nearshore kelp forest fish assemblage, primarily of the genusSebastes, accounted for 96% of the observed mortalities andS. mystinus (blue rockfish) alone accounted for 72%.     

Effects of El Niño-related Drought on Freshwater and Brackish-water Fishes in Suriname, South America

Droughts associated with the El Niño-Southern Oscillation (ENSO) affected fishes of brackish-water lagoons, freshwater swamps and a rainforest creek in Suriname, South America. The mean rainfall in the period August to February in 22 El Niño years was 76.6% of the mean rainfall in the same months of non-El Niño years. In the period 1900–1999, three out of four years in which an extreme drought (rainfall less then 60% of the mean value) occurred were El Niño years. The recent 1997/1998 ENSO event caused the second most severe drought in a 100-year record. Drying up of brackish-water lagoons, freshwater swamps and rainforest creeks was observed during El Niño-related droughts. In the lagoons ariid catfish died first, followed by snook, tilapia, mullet and tarpon, respectively. Landings of lagoon fish were positively correlated with rainfall in the period August–February. During the El Niño-related drought we observed failure of reproduction in three species of callichthyid armoured catfish in both coastal freshwater swamps and a rainforest creek in the interior. In the El Niño year 1997/1998, the no flow period of the rainforest creek was extended by four months beyond the long dry season and the dissolved oxygen levels in the dry-season pools dropped to 1.27mg O₂l^–1 (as compared to 4.53mg O₂l^–1 under running water conditions). Other fish species of the rainforest creek also showed decreased reproductive success in the El Niño year. We suggest that the stochastic effects of El Niño-related drought may be an important non-equilibrium component in the ecology of neotropical inland fish communities.     

Contrasting demographies and persistence of rare annual plants in highly variable environments

Spatial and temporal variation in critical life history traits differ markedly between two co-occurring, rare and endangered annual plants, Gilia tenuiflora arenaria and Chorizanthe pungens pungens, that have restricted, but overlapping geographic distributions in coastal habitats of central California, USA. Environmental variation was extreme during the 6-year study (1997–2002), with the greatest differences between an intense wet, warm El Niño year (1998), followed by a very dry, cool La Niña (1999). Both species have similar increases in adult survival and seed set with wetter, warmer weather in spring, but they differed in other traits: more Gilia germinated in years with high rainfall and temperature, while more Chorizanthe germinated in dry, cooler years; Gilia abundance increased with the number of years since the previous large El Niño event, while Chorizanthe abundance declined; and Gilia abundance was independent of the previous year’s seed set, while Chorizanthe density was directly related to the previous year’s seed set. The strong negative associations of Chorizanthe abundance with warm, wet weather and with time since the previous El Niño probably reflect the particular sequence of annual weather patterns from 1997 through 2002, especially the extremes in 1998 and 1999. Since it germinates readily in most years under a wide range of winter conditions and does not develop a long-lived seed bank, Chorizanthe seedling abundance reflects recent additions and depletions of its seed bank, rather than prevailing weather, per se. In contrast, Gilia seeds may remain in the seed bank for many years, until relatively rare winter conditions trigger significant germination. These species-specific demographies enhance persistence and coexistence of these species, but the mechanisms differ from each other and from those described for annuals in other highly variable environments.     

A possible relationship between outbreaks of the oriental migratory locust (Locusta migratoria manilensis Meyen) in China and the El Niño episodes

We investigated the statistical relationship between outbreaks of the oriental migratory locust (Locusta migratoria manilensis Meyen) in the Huang Ho and Huai Ho regions of China and El Niño episodes during 1905–1959, and discussed how El Niño affects locust outbreaks. The outbreaks of the locust mostly occurred 1–2 years after the El Niño episodes. El Niño was suggested to affect the locust outbreaks by changing the precipitation and air temperature in Northern China.     

El Niño episodes coincide with California moray Gymnothorax mordax settlement around Santa Catalina Island,California

The hypothesis that El Niño events influence the settlement patterns of the California moray Gymnothorax mordax is tested. The pelagic larval duration (PLD) of larval G. mordax is unknown, but studies on leptocephalus of related species suggest that larvae are long‐lived, up to 2 years. Gymnothorax mordax, an elusive predatory species and the only muraenid off the coast of California, is considered abundant in the waters around Catalina Island. Thirty‐three individuals were collected from Two Harbors, Catalina Island, and otoliths were taken to provide estimates of their age. Settlement year for each individual was backcalculated using estimated age from otolith measurements. These ages were then cross referenced with the Oceanic Niño Index (ONI) developed by the National Oceanographic and Atmospheric Administration (NOAA) to correlate estimated age of settlement with known El Niño years. Of the 33 individuals collected, 30 settled at Catalina Island during El Niño years. The oldest individual in the data‐set was 22 years old, placing G. mordax as one of the longer‐lived predatory fishes in the system. The present study represents the first account of wild G. mordax ages and suggests that El Niño events have an important role in driving the settlement of recruits towards the northern edge of their range.     

Egg production rates of eight calanoid copepod species during summer 1997 off Newport, Oregon, USA

Measurements of hydrography, water transparency, chlorophyll (Chl) a and egg production rates (EPRs) by females of Calanus marshallae Frost, Calanus pacificus Brodsky, Eucalanus californicus Johnson, Epilabidocera longipedata Sato, Pseudocalanus mimus Frost, Centropages abdominalis Sato, Acartia longiremis Lilljerborg and Paracalanus parvus (Claus) were estimated at weekly intervals between 17 July and 2 September 1997. Production of eggs was determined in 24 h incubations to examine the effects of environmental variability on EPR, to detect the possibility of food limitation of EPR, and to evaluate the hypothesis that growth rates of females are size dependent. During the study, an anomalous downwelling event occurred, possibly in response to the 1997 El Niño, which allowed us to determine how El Niño events affect EPRs of coastal copepods. The larger copepods Calanus marshallae, Calanus pacificus and Centropages abdominalis showed the highest egg production and specific growth rates during the period of active upwelling (18 July-13 August, water temperatures 8-13C, Chl a concentration 4.7-16.2 l^-1 and water transparency 3-5 m). After 27 August, the 1997-98 El Niño arrived off Oregon, creating a downwelling situation. Upwelling winds ceased, the thermocline intensified, temperature and transparency increased (to >18°C and 16 m), and Chl a declined to <2 g l^-1. Densities of the common coastal species declined greatly as well. Paracalanus parvus became the dominant species, and Eucalanus californicus, Epilabidocera longipedata and Corycaeus anglicus became common in our samples. EPRs for the larger boreal copepods (Calanus and Centropages) declined greatly during El Niño;; the smaller copepods, Pseudocalanus mimus, A.longiremis and Paracalanus parvus, showed low but relatively constant egg production and specific growth rates during both upwelling and downwelling events. Over the entire study period, only three species produced eggs at its maximum rate (24-28 eggs female^-1 day^-1), Pseudocalanus mimus which averaged 4 eggs day^-1. All other species had EPRs that were two or five times below their maximum EPR. Thus, EPRs were not related to body size, contrary to our expectations. Hatching success was variable among species. Values as low as 20-40% were found for all species at least once during the study period, suggesting that occasionally a substantial portion of egg production may not be viable.      

Climate variation and El Niño-Southern Oscillation events on the Great Barrier Reef: 1958 to 1987

Seasonal and inter-annual variation of several surface climate variables near the Great Barrier Reef (GBR) are described for the 30-year period, 1958–1987. Large inter-annual variability of rainfall and river flow in coastal Queensland is linked to the aperiodic influences of El Niño-Southern Oscillation events. These events also affect sea surface temperature and wind fields, though the inter-annual variability of these variables is not as large as rainfall and river flow. The major impacts on waters of the GBR appear to be greatly increased freshwater inputs, reduced surface radiation (and thus light levels) and enhanced tropical cyclone activity during anti-El Niño events. El Niño events have less effect on climate of the GBR because they tend to maintain winter-like conditions. The effects of this background of high variability in the physical environment on reef processes must be considered when examining changes in such processes, changes in climate (e.g. due to global warming) or increases in anthropogenic impacts.     

A comparison of genetic diversity between the Galápagos Penguin and the Magellanic Penguin

The Galápagos Penguin (Spheniscusmendiculus) is a United States federallylisted endangered species with populations onthe Galápagos Islands of Fernandina andIsabela. Although the waters around theislands are normally productive, lowproductivity during El Niño years resultsin high adult penguin mortality and lowrecruitment in following years. We usedmicrosatellite markers developed for Spheniscus penguins to study the long termgenetic effects of serial bottleneck events inthe Galápagos Penguin, and compared thisvariation to that of its congener, theMagellanic penguin (Spheniscusmagellanicus). The observed heterozygosityfor the Galápagos Penguin was 3%,significantly lower than the 46%heterozygosity of the Magellanic Penguin. Thislow level of heterozygosity is directly relatedto its low effective population size. Whilethis population has survived long term,presumably without high levels of geneticvariation, we feel that the greater frequencyof El Niño events, coupled with increasedhuman impacts such as introduced disease, oildischarge, and competition with fisheries, mayput the species in particular danger ofextinction.     

Phytoplankton phenology in the global ocean

In recent years, phytoplankton phenology has been proposed as an indicator to monitor systematically the state of the pelagic ecosystem and to detect changes triggered by perturbation of the environmental conditions. Here we describe the phenology of phytoplankton growth for the world ocean using remote-sensing ocean colour data, and analyse its variability between 1998 and 2007. Generally, the tropics and subtropics present long growing period (≈15-20 weeks) of low amplitude (<0.5 mg Chl m⁻³), whereas the high-latitudes show short growing period (<10 weeks) of high amplitude (up to 7 mg Chl m⁻³). Statistical analyses suggest a close coupling between the development of the growing period and the seasonal increase in insolation in the North Atlantic and Southern Ocean. In the tropics and subtropics, variability in light is low, and the growing period is controlled by nutrient supply occurring when mixing increases. Large interannual variability in the duration of the growing period is observed over the decade 1998-2007, with positive anomalies following the major 1997-1998 El Niño-La Niña events, and generally negative anomalies from 2003 to 2007. Warmer Sea-Surface Temperature (SST) over the duration of the growing period is associated with longer duration at high-latitudes indicating an extension of the growing period over summer months. The opposite is observed in the tropics and subtropics, where the duration is shorter when the SST is warmer, indicating increased stratification. Positive phases of North Atlantic Oscillation and Southern Annular Mode and negative phases of Multivariate El Niño-Southern Oscillation index (El Niño conditions), associated with enhanced water mixing and nutrients supply, generally sustain longer growth. On the basis of the results, perspectives are drawn on the utility of phenology as an organising principle for the analysis of pelagic ecosystem.