Algal class abundances,estimated from chlorophyll and carotenoid pigments,in the western Equatorial Pacific under El Niño and non-El Niño conditions

Phytoplankton samples were collected from the equatorial Pacific (10°S to 10°N along 155°E) in June 1992 as part of the Australian contribution to the JGOFS program. Chlorophyll and carotenoid pigments were measured by HPLC, and a PC-based computer program (CHEMTAX) was used to estimate the contribution of 9 algal classes to the total chlorophyll a concentration in 9 separate depth bands at each location. This cruise occurred in the middle of the prolonged 1991/1993 El Niño, and the results are compared with similar data from a cruise in October 1990 which occurred before this El Niño but after the 1988/1989 La Niña.Changes in the pigment : chlorophyll a ratios appeared consistent across algal classes and, apart from some minor exceptions, consistent between cruises. Pigments involved in light-harvesting generally increased relative to chlorophyll a with increasing depth, whereas the ratio for photoprotective pigments (e.g. diadinoxanthin) usually decreased with depth. The zeaxanthin concentration per cell for cyanobacteria decreased with depth in the surface 75 m during 1992 as would be expected for a photoprotective pigment.Based on their contribution to the total chlorophyll a concentration, haptophytes, prochlorophytes, cyanobacteria (Synechococcus) and chlorophytes were the dominant algal classes in 1992. The chlorophyte contribution to chlorophyll a in 1992 (14.8%) was almost double that in 1990 (7.8%). This increase was largely at the expense of the cyanobacteria and haptophytes, which both decreased significantly. The increase in chlorophytes in 1992 was particularly noticeable in the surface waters south of the equator at about 4°S, where there was evidence of upwelling.     

Research on the spectral analysis and test method of period signals in monthly mean sea level

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Analysis of the cause and effect relationships between El Niño in the Pacific and its analog in the equatorial Atlantic

The relations between the processes occurring in the equatorial latitudes of the Pacific and Atlantic oceans were studied on the basis of the Granger causality analysis and a simulation of phase dynamics using the indices of the El Niño-Southern Oscillation (ENSO) and the equatorial Atlantic mode (EAM). Data on the monthly means of the sea-surface temperature over the period 1870–2006 for the Niño 3 (5° S-5° N, 150° W-90° W) and Niño 3.4 (5° S-5° N, 170° W-120° W) regions in the Pacific and the Atlantic 3 region (20° W-0, 3° S-3° N) in the Atlantic Ocean were used as the ENSO and EAM indices. The statistically significant influence of the EAM on the ENSO is noted. The lag time of this influence is estimated at two months. No significant reverse effect is revealed. An increase in the EAM’s influence on the ENSO was observed in the second half of the 20th century.     

Variability of the meridional transport processes in the Southern Ocean and its possible relation to El Niño

The article deals with the influence of wind and atmospheric pressure on the barotropic variability of the Antarctic Circumpolar Current (ACC). This effect is studied using a global barotropic model under idealized and realistic atmospheric forcings. The results of barotropic modeling demonstrate that variations in the wind forcing over the ACC, together with the effects of the topography and coastline, lead to the variability in the meridional water flux in the Southern Ocean. The variability of these fluxes is negatively correlated with the wind strength over the ACC. A possible link between the short-period variability of the water flux in the Pacific sector of the Southern Ocean and El Niño is demonstrated using 3D ocean modeling and correlation analysis. It is shown that the variability of the meridional water flux caused by atmospheric perturbations over the ACC can lead to short-period density anomalies in the Southern Ocean north of 47°S, which later can be transferred to low latitudes by means of the wave mechanism described in [15] and strongly influence the tropical region.     

A comparison of remote vs. local influence of El Niño on the coastal circulation of the northeast Pacific

A set of spatially nested circulation models is used to explore interannual change in the northeast Pacific (NEP) during 1997–2002, and remote vs. local influence of the 1997–1998 El Niño on this region. Our nested set is based on the primitive equations of motion, and includes a basin-scale model of the north Pacific at ∼40-km resolution (NPac), and a regional model of the Northeast Pacific at ∼10-km resolution. The NEP model spans an area from Baja California through the Bering Sea, from the coast to ∼2000-km offshore. In this context, “remote influence” refers to effects driven by changes in ocean velocity and temperature outside of the NEP domain; “local influence” refers to direct forcing by winds and runoff within the NEP domain. A base run of this model using hindcast winds and runoff for 1996–2002 replicates the dominant spatial modes of sea-surface height anomalies from satellite data, and coastal sea level from tide gauges. We have performed a series of sensitivity runs with the NEP model for 1997–1998, which analyze the response of coastal sea level to: (1) hindcast winds and coastal runoff, as compared to their monthly climatologies and (2) hindcast boundary conditions (from the NPac model), as compared to their monthly climatologies. Results indicate penetration of sea-surface height (SSH) from the basin-scale model into the NEP domain (e.g., remote influence), with propagation as coastal trapped waves from Baja up through Alaska. Most of the coastal sea-level anomaly off Alaska in El Niño years appears due to direct forcing by local winds and runoff (local influence), and such anomalies are much stronger than those produced off California. We quantify these effects as a function of distance along the coastline, and consider how they might impact the coastal ecosystems of the NEP.     

Frequency of Summer Atmospheric Blockings in the Northern Hemisphere in Different Phases of El Niño and Pacific Decadal and Atlantic Multidecadal Oscillations

Izvestiya, Atmospheric and Oceanic Physics - Regional anomalies in the frequency of atmospheric blockings in the Northern Hemisphere detected on the basis of reanalysis data since 1979 during...     

Land use effects on habitat,water quality,periphyton, and benthic invertebrates in Waikato,New Zealand,hill‐country streams

Water quality, habitat, and biota were compared during spring amongst c. 100 m reaches on 11 streams draining pasture, native (podocarp‐broadleaf) forest, and exotic pine forest established on pasture 15 years previously. Differences were greatest between the pasture and native forest streams. Only 1–3% of incident light reached native and pine forest streams whereas 30% reached pasture streams. Pasture streams had 2.2°C higher mean temperature than the native streams, and 5‐fold higher nitrate, 30‐fold higher algal biomass, and 11‐fold higher gross photosynthesis. Native streams were 60% wider than pasture, with pine streams intermediate. Pine and pasture streams had 3‐fold higher suspended solids and fine sediment stored in the streambed than native streams. Woody debris volume was 17‐fold greater in pine than pasture streams, with native streams intermediate. Invertebrate taxa richness did not differ between land uses. Community composition differed most between pasture and native forest, with pine forest streams intermediate. Invertebrate densities were 3‐fold higher in pasture than native streams, mainly because of more chironomids and snails, but mayflies, stoneflies, and caddisflies densities were 2–3‐fold higher in forest streams than pasture.     

Length‐mass models for some common New Zealand littoral‐benthic macroinvertebrates,with a note on within‐taxon variability in parameter values among published models

Regression models are developed and presented to predict dry mass (mg) from two linear dimensions (mm) for 17 benthic macroinvertebrate taxa common to littoral zones of New Zealand lakes. We also provide regression models to predict body length from head capsule width for the major insect taxa. Dry mass was best explained as a power function of all linear dimensions: M = aL _b .Parameters are presented in the log₁₀‐transformed linear form of this power function. Body length was a simple linear function of head capsule width for all insect taxa, hence parameters for these models are presented as untransformed values. We also provide family level models for the Chironomidae, and compare our chironomid body length‐mass model with other published Chrionomidae length‐mass models. There was a very high degree of variability in parameter values among published length‐mass models for the family Chironomidae (mean coefficient of variation for mass at length = 148%). We discuss the potential causes and implications of this variability.     

A note on the fauna of a ripple‐marked sandy sediment in western cook strait,New Zealand

Photographs of a ripple‐marked sea bed are reproduced together with the results of a mechanical analysis of the sediment and a list of the animals found. The sparseness of the fauna is attributed to the mobility of the substrate.     

Drift currents in the southern New Zealand region as derived from Lagrangian measurements and the remote sensing of sea‐surface temperature distributions

Four drift bottles, cast adrift south of the Subtropical Convergence at 48°S, 156°E in November 1980, landed within 123 days of release at a short stretch of coast north of Banks Peninsula. A high degree of coherence in the responsible drift pattern is indicated. The contemporary surface circulation inferred from satellite‐derived sea‐surface temperature distributions indicates that the bottles were entrained in a meridionally‐converging flow after drifting across the southern Tasman Sea without crossing the Convergence. They were prevented from further eastward drifting because of a marked southward flexing of the Convergence east of the Southland Current during February 1981. Because of local weather and tide effects, the bottles finally beached in Pegasus Bay.     

Coastal upwelling along the north coast of Papua New Guinea and SST cooling over the pacific warm pool: A case study for the 2002/03 El Niño event

We investigate an overlooked mechanism—coastal upwelling—for sea surface temperature (SST) cooling in the western side of the mean location of the Pacific warm pool (WSWP: 5°S–5°N, 140°E–150°E) prior to El Niño onset. We analyze various observed data such as the TRIangle Trans-Ocean buoy Network (TRITON) moored buoy data, Conductivity-Temperature-Depth (CTD) data, satellite data and a hindcast experiment output by a high-resolution ocean general circulation model (OGCM). We focus on the precondition of the 2002/03 El Niño event, for which many datasets are available. Relatively cool water upwelled along the north coast of Papua New Guinea (PNG) during December 2001, prior to the onset of the 2002/03 El Niño event, and then spread out over a wider area to the northeast. Simultaneously, strong west-northerly surface winds occur along the north coast. Heat budget analysis of TRITON buoy data in the WSWP reveals that negative zonal heat advection due to eastward current is the main factor for cooling the mixed layer in the WSWP in contrast to the warming effect of the surface heat flux during the period. This cooling requires a source of colder water to the west. Similar analysis of OGCM outputs also suggests that the upwelled relatively cool water along the PNG north coast, and its northeastward extension to the equatorial region, contributes to cooling of the surface water over the WSWP mainly via negative zonal heat advection. Similar mechanisms are confirmed also for the 1982/83 and 1997/98 El Niño events by analyses of OGCM outputs and historical SST data. The low SST in the WSWP generated a positive zonal SST gradient together with high SST east of the WSWP. It may contribute to enhancement of the westerly surface wind in this region, leading to the onset of the 2002/03 El Niño event.     

Photo‐identification of short‐beaked common dolphins (Delphinus delphis) in north‐east New Zealand: A photo‐catalogue of recognisable individuals

Photo‐identification has been established as a helpful tool in cetacean research. However, no study to date has attempted to apply this method to short‐beaked common dolphins (Delphinus delphis L.). We present here the results of two studies that were conducted concurrently in Mercury Bay and the Hauraki Gulf on the north‐east coast of New Zealand's North Island. Methods for distinguishing between individual dolphins are discussed. Sighting records of recognisable individuals indicate that some common dolphins move between Mercury Bay and the Hauraki Gulf (100 km distance), as well as between Mercury Bay and Whakatane (200 km distance). Common dolphin abundance and site fidelity appeared to be greater in the Hauraki Gulf than in Mercury Bay. A selection of photographs of distinct individuals is presented to allow future studies to compare their sighting records to ours, which may help establish the extent of home ranges, site fidelity, and possibly even longevity for common dolphins.     

Snapper tagging in north‐east New Zealand, 1974: Analysis of methods,return rates,and movements

During 1974, 5045 snapper Chrysophrys auratus (Forster) were tagged at various locations along the north‐east coast of the North Island. Most were trawl‐caught using a canvas cod‐end in shallow inshore areas. Four types of tags were used, of which two were found to be effective: a large single‐barbed dart tag, and a lock‐on spaghetti tag. For the period up to the end of October 1975, 88 (1.74%) were returned. Highest returns were from the Hauraki Gulf (2.3%) and lowest from Northland (nil). Analysis of the recapture data showed that most movements were local, with a mean distance between tagging site and recapture position of 13.9 nautical miles (25.7 km). Four movements greater than 50 miles (92.6 km) were recorded. Local movements in the Hauraki Gulf were associated with the spring/summer spawning period. This movement, out from inshore areas which are closed to seiners and trawlers, and schooling behaviour, are thought to be the main factors contributing to the peak in snapper catches at this time of the year.     

Correction to: El Niño-related sea surface elevation and ocean bottom pressure enhancement associated with the retreat of the Oyashio southeast of Hokkaido,Japan

Marine Geophysical Research - In the original publication, the Fig. 2 was published incorrectly. The correct version (Fig. 2) is given in this correction. The original article has been...     

Assessment of reprocessed sea surface height measurements derived from HY-2A radar altimeter and its application to the observation of 2015–2016 El Ni?o

Haiyang-2A(HY-2A) is China's first ocean dynamic environment satellite and the radar altimeter is one of its main payloads. One of the main purposes of the radar altimeter is to measure the sea surface height(SSH). The SSH determined from the altimeter range measurements includes some range and geophysical corrections. These corrections largely affect the accuracy of the SSH measurements. The range and the geophysical corrections are reprocessed and the altimeter waveforms in HY-2A sensor interim geophysical data set records(S-IGDR) are retracked from June 1, 2014 to June 14, 2014, and the accuracy of the reprocessed SSH measurements is evaluated.The methods of the range and geophysical corrections used to reprocess HY-2A altimeter data are validated by using these methods to reprocess the Jason-2 range and geophysical corrections and comparing the results with the range and geophysical corrections in Jason-2 geophysical dataset records(GDR) product. A crossover analysis is used to evaluate the accuracy of the reprocessed HY-2A SSH measurements. The standard deviation(STD) of the crossover SSH differences for HY-2A is around 4.53 cm while the STD of the SSH differences between HY-2A and Jason-2 is around 5.22 cm. The performance of the reprocessed HY-2A SSH measurements is significantly improved with respect to the SSH measurements derived from HY-2A interim geophysical dataset records(IGDR)product. The 2015–2016 El Ni?o has been the strongest El Ni?o event since 1997–1998. The range and the geophysical corrections in HY-2A IGDR are reprocessed and sea level anomalies are used to monitor the2015–2016 El Ni?o. The results show that the HY-2A altimeter can well observe the 2015–2016 El Ni?o.     

Postal surveys of anglers fishing for sea‐run Chinook salmon on the Rakaia River,Canterbury, New Zealand, 1973/74 and 1974/75.

Postal probability surveys were used to estimate the angler catch of salmon, and the number of anglers fishing for salmon, on the Rakaia River, Canterbury, New Zealand, for the seasons 1973/74 and 1974/75. Response levels of over 97% were obtained. An estimated 3531 fish were caught by an estimated 4405 anglers in 1973/74 and 4875 fish by 5332 anglers in 1974/75. The sample catch frequency distributions returned were highly positively skewed with few anglers catching most of the fish. The effect of this skewness on the estimate of total catch was investigated by bootstrapping and confidence intervals thus set were compared to those derived from the Gaussian assumption. Confidence limits were obtained for the estimate of number of anglers.     

“Living with our backs to the sea”: A critical analysis of marine and coastal governance in Guatemala

Guatemala's rich coastal and marine biodiversity provides essential ecosystem goods and services to local residents and the national economy through artisanal and commercial fisheries, aquaculture, port exports and, to a lesser extent, tourism. As in many other countries, national policies emphasise the significance of marine conservation and marine resources, primarily through implementing marine protected areas (MPAs). However, this assumes that governance, as reflected in legal, institutional and organizational frameworks, political capacity and human resources is sufficiently developed to ensure MPAs meet these goals. These issues are explored through presenting the first detailed analysis of coastal and marine governance in Guatemala. The research highlights a range of barriers to good governance which restrict the extent to which MPAs can function effectively. Recommendations are made which can capitalise upon the potential for locally managed marine areas as a means to facilitate the improved governance of coastal and marine resources in Guatemala.     

The Indian Ocean’s asymmetric effect on the coupling of the Northwest Pacific SST and anticyclone anomalies during its spring–summer transition after El Niño

By comparing different climatologies in El Niño decaying summer with regard to the presence of Indian Ocean Basin (IOB) warming, we studied the effect of IOB warming on the Northwest Pacific sea surface temperature (SST) anomalies and the coupling process with the surface wind. Zonal asymmetric coupling feedback in the west and east of the Northwest Pacific were caused by the asymmetric spring–summer transition of the background tropical atmospheric circulation. Although the westward wind anomaly caused by the remote effect of IOB warming is found in the whole Northwest Pacific, reversal of the mean background surface winds in the western part leads to negative wind-evaporation SST (WES), whereas sustained trade winds lead to positive WES in the eastern part. The east–west SST gradient resulting from this zonal asymmetric evolution of SST sets off more positive feedback that strengthens the local anticyclone easterly anomalies.     

Bacterial production of anomalously high dissolved sulfate concentrations in Peru slope sediments: steady-state sulfur oxidation,or transient response to end of El Niño?

Concentrations of dissolved sulfate and sulfur isotopic ratios of dissolved sulfide in surface sediments of the Peru shelf and upper slope indicate that the sediments can be divided into two depth intervals based on the dominant biogeochemical reactions. Although rates of bacterial sulfate reduction are high throughout Peru surface sediments, chemistry of the upper interval (<10–20 cm) is dominated by chemoautotrophic oxidation of dissolved sulfide and elemental sulfur, while the lower interval (>10–20 cm) is dominated by dissimilatory sulfate reduction. In three of the four cores examined here, pore water concentrations of sulfate in the top 10 cm of the sediment are significantly higher than those of the overlying seawater. Peak sulfate concentrations in pore water (37–53 mmol/l) are ∼1.3–1.9 times that of seawater sulfate and are located 1–6 cm below the sediment/water interface (SWI). The excess sulfate is most likely produced by oxidation of elemental sulfur coupled to reduction of nitrate, a reaction mediated by a facultative chemoautotrophic sulfide-oxidizing bacterium, Thioploca spp. Numerical simulations demonstrate that the anomalously high concentrations of dissolved sulfate can be produced by steady-state or non-steady-state processes involving high rates of bacterial oxidation of elemental sulfur. If bacterial sulfur oxidation is a transient phenomenon, then it is probably triggered by seasonal or El Niño-induced changes in water-column chemistry of the Peru undercurrent.