Introduction to the PICES practical workshop: objectives,overview of the study area,and projects conducted by the participants

We coordinated a collaborative research project to investigate environmental conditions in Vancouver Harbour, British Columbia, Canada, between 23 May and 7 June 1999. This special volume of Marine Environmental Research presents a collection of papers giving results of these studies. The project was part of a practical workshop sponsored by the Marine Environmental Quality (MEQ) committee of the North Pacific Marine Science Organization (PICES). Twenty-four scientists from PICES countries (USA, Canada, Russia, Japan, Korea, and China) participated. A wide variety of data was collected, including community structure of benthic invertebrates and fish, evaluation of fish health using biological markers and exposure data, evaluation of contaminant exposure in inter-tidal invertebrates, imposex in gastropods, and information about natural toxins produced by algae. The workshop provided an opportunity for PICES participants to gain an improved appreciation of the approaches and techniques used by other member countries to assess the effects of marine pollution. The purpose of this introductory paper is to briefly describe the project, provide background information on how it was organized, and give an overview of our knowledge about the harbour's environment.     

Use of ultrasonic telemetry to determine the area of bait influence and trapping area of American lobster,Homarus americanus,traps

Using ultrasonic telemetry, we measured the distance of attraction to a baited trap and then used this value to calculate the “area of bait influence”. This value, along with the mean daily home range for the same animals, was used to calculate the “trapping area” of an individual trap. Lobsters (n = 25) were tracked inside a large underwater mesocosm containing a single baited lobster trap. During the study, 14 of the 25 lobsters approached the trap from a mean (+SEM) distance of 11.0 ± 0.7 m. Using this distance as the radius of a circle, the resulting circular area of bait influence was 380 m². The movements of 18 lobsters were used to calculate a mean daily home range of 1002.4 ± 195.7 m². The radius of a circle with this area (17.8 m) was then combined with the mean distance of bait attraction to calculate the trapping area, defined as: the total area from which the catch is drawn (2604.0 m²; a circle with a radius of 28.8 m or 17.8 m + 11.0 m). A demonstration of the potential use of empirical data about lobster home ranges, trap dynamics and area of bait influence to improve our understanding of the relationship between the density of lobsters on the bottom and catch is included.     

Changes in water quality following tidal inundation of coastal lowland acid sulfate soil landscapes

This study examines the remediation of surface water quality in a severely degraded coastal acid sulfate soil landscape. The remediation strategy consisted of partial restoration of marine tidal exchange within estuarine creeks and incremental tidal inundation of acidified soils, plus strategic liming of drainage waters. Time-series water quality and climatic data collected over 5 years were analysed to assess changes in water quality due to this remediation strategy. A time-weighted rainfall function (TWR) was generated from daily rainfall data to integrate the effects of antecedent rainfall on shallow groundwater levels in a way that was relevant to acid export dynamics. Significant increases in mean pH were evident over time at multiple monitoring sites. Regression analysis at multiple sites revealed a temporal progression of change in significant relationships between mean daily electrical conductivity (EC) vs. mean daily pH, and TWR vs. mean daily pH. These data demonstrate a substantial decrease over time in the magnitude of creek acidification per given quantity of antecedent rainfall. Data also show considerable increase in soil pH (2–3 units) in formerly acidified areas subject to tidal inundation. This coincides with a decrease in soil pe, indicating stronger reducing conditions. These observations suggest a fundamental shift has occurred in sediment geochemistry in favour of proton-consuming reductive processes. Combined, these data highlight the potential effectiveness of marine tidal inundation as a landscape-scale acid sulfate soil remediation strategy.     

A new method for spatial centrographic analysis of mineral deposit clusters

A centrographic method for analysing mineral deposit clusters is illustrated using the komatiite-hosted Kambalda nickel sulphide deposit cluster, Yilgarn craton, Western Australia. In this method, the standard distance circle divides the cluster into a more endowed inner part and a less endowed peripheral part. The standard deviational ellipse, another centrographic object, depicts the preferred northwest–southeast trend of nickel orebodies at Kambalda. Weighted centrography shows that nickel endowment is greater in the eastern than western part of the cluster. The spatio-geometric interaction of the circle and ellipse splits the cluster into several partitions. The relative concentration of nickel orebodies or endowment within a partition in relation to their concentration within the entire cluster is termed ‘capture efficiency’. Komatiite areal trace exhibits higher nickel orebody capture efficiency than spatio-geometric partitions; however, some spatio-geometric partitions exhibit nickel endowment capture efficiencies comparable to that of komatiite. Furthermore, nickel orebody and endowment capture efficiencies of komatiite are elevated only within the standard distance circle. These results suggest that at Kambalda, (i) the standard distance circle is a prime window for understanding the komatiite-hosted nickel system, and (ii) spatio-geometric partitions are plausible locales for spatial analysis of nickel orebodies and endowment. The proposed centrographic method is potentially useful in mineral resource estimations and mineral exploration targeting.     

Geomorphic and stratigraphic evidence for an unusual tsunami or storm a few centuries ago at Anegada, British Virgin Islands

Waters from the Atlantic Ocean washed southward across parts of Anegada, east-northeast of Puerto Rico, during a singular event a few centuries ago. The overwash, after crossing a fringing coral reef and 1.5?km of shallow subtidal flats, cut dozens of breaches through sandy beach ridges, deposited a sheet of sand and shell capped with lime mud, and created inland fields of cobbles and boulders. Most of the breaches extend tens to hundreds of meters perpendicular to a 2-km stretch of Anegada??s windward shore. Remnants of the breached ridges stand 3?m above modern sea level, and ridges seaward of the breaches rise 2.2?C3.0?m high. The overwash probably exceeded those heights when cutting the breaches by overtopping and incision of the beach ridges. Much of the sand-and-shell sheet contains pink bioclastic sand that resembles, in grain size and composition, the sand of the breached ridges. This sand extends as much as 1.5?km to the south of the breached ridges. It tapers southward from a maximum thickness of 40?cm, decreases in estimated mean grain size from medium sand to very fine sand, and contains mud laminae in the south. The sand-and-shell sheet also contains mollusks??cerithid gastropods and the bivalve Anomalocardia??and angular limestone granules and pebbles. The mollusk shells and the lime-mud cap were probably derived from a marine pond that occupied much of Anegada??s interior at the time of overwash. The boulders and cobbles, nearly all composed of limestone, form fields that extend many tens of meters generally southward from limestone outcrops as much as 0.8?km from the nearest shore. Soon after the inferred overwash, the marine pond was replaced by hypersaline ponds that produce microbial mats and evaporite crusts. This environmental change, which has yet to be reversed, required restriction of a former inlet or inlets, the location of which was probably on the island??s south (lee) side. The inferred overwash may have caused restriction directly by washing sand into former inlets, or indirectly by reducing the tidal prism or supplying sand to post-overwash currents and waves. The overwash happened after A.D. 1650 if coeval with radiocarbon-dated leaves in the mud cap, and it probably happened before human settlement in the last decades of the 1700s. A prior overwash event is implied by an inland set of breaches. Hypothetically, the overwash in 1650?C1800 resulted from the Antilles tsunami of 1690, the transatlantic Lisbon tsunami of 1755, a local tsunami not previously documented, or a storm whose effects exceeded those of Hurricane Donna, which was probably at category 3 as its eye passed 15?km to Anegada??s south in 1960.     

Seasonal variation in standing crop of the seagrassSyringodium filiforme and associated macrophytes in the Northern Indian River,Florida

Seasonal variation in the standing crop of the seagrassSyringodium filiforme and its associated macrophytes was studied in a northern basin of the Indian River, a large mesohaline lagoon in central Florida, near the northern distributional limit ofS. filiforme. The minimum standing crop occurred from February through April and the maximum in September. Two other seagrasses,Halodule wrightii andHalophila engelmannii, together with a drift algal community, occurred in the study quadrat, but were not major components of the macrophytic system. The formation of sizeable sandy patches within Indian River seagrass beds is partially due to the burrowing activities ofLimulus polyphemus. Thermal stresses associated with the northern geographicalS. filiforme range may contribute to this phenomenon by restricting annual production, hence limiting patch regrowth.     

Ecological Signatures of Anthropogenically Altered Tidal Exchange in Estuarine Ecosystems

One of the most conspicuous anthropogenic disturbances to estuaries worldwide has been the alteration of freshwater and tidal influence through the construction of water control structures (dikes, tide gates, culverts). Few studies have rigorously compared the responses of differing groups of organisms that serve as contrasting conservation targets to such anthropogenic disturbances in estuarine ecosystems. Elkhorn Slough in central California includes a spectrum of tidally restricted habitats behind water control structures and habitats experiencing full tidal exchange. To assess community composition for several different taxa in habitats with varying tidal exchange, we employed a variety of field approaches and synthesized results from several different studies. Overall, we found that communities at sites with moderately restricted tidal exchange were fairly similar to those with full tidal exchange, but those with extremely restricted tidal exchange were markedly different from other categories. These differences in community composition are likely the result of several factors, including restricted movement due to physical barriers, differences in water quality characteristics, and differences in habitat structure. Indeed, in this study, we found that water quality characteristics strongly vary with tidal restriction and may strongly influence patterns of species presence or absence. We also found that different conservation targets showed contrasting responses to variation in tidal exchange. Full exchange appears to favor native oysters, commercially valuable flatfish, migratory shorebirds, and site-level biodiversity. Minimal tidal exchange due to water control structures supports a suite of estuarine endemics (including the tidewater goby and California brackish snail) not represented elsewhere and minimizes invasions by non-native marine species. Altogether, our results suggest that total estuary-wide biodiversity may be enhanced with a mosaic of tidal exchange regimes.     

Ultraviolet Laser Sampling and High Resolution Inductively Coupled Plasma-Mass Spectrometry of NIST and BCR-2G Glass Reference Materials

A Merchantek LUV266 ^TM petrographic ultraviolet (UV) laser microprobe has been used in conjunction with a Finnigan MAT ELEMENT ^TM high resolution ICP double-focusing mass spectrometer (HR-ICP-MS) for solid microsampling and geochemical analysis. This new configuration for laser ablation has the advantage of coupling the high sensitivity and fast scanning technology applied in the ELEMENT with the ablation efficiency of a UV laser. Optimisation of the configuration on the synthetic NIST SRM 612 glass standard reference material using Q-switched UV laser energy of 2 mJ and a 5 Hz repetition rate demonstrates: (1) a linear element response factor throughout the mass spectrum, suggesting limited fractionation during laser ablation; (2) a high sensitivity and very low background noise for most elements of interest; (3) limits of detection ranging from 3 ng g-1 for Sc to 300 pg g-1 for U; (4) a flat topped peak shape suitable for precise isotopic measurements; and (5) a flat bottomed crater geometry which permits progressive ablation for the analysis of thin sections. Average precision and accuracy estimates based on replicate analyses of synthetic NIST standard reference material and USGS BCR-2G glasses are below 10% for most elements.     

Post-glacial regional climate variability along the East Antarctic coastal margin—Evidence from shallow marine and coastal terrestrial records

We review the post-glacial climate variability along the East Antarctic coastline using terrestrial and shallow marine geological records and compare these reconstructions with data from elsewhere. Nearly all East Antarctic records show a near-synchronous Early Holocene climate optimum (11.5–9 ka BP), coinciding with the deglaciation of currently ice-free regions and the optimum recorded in Antarctic ice and marine sediment cores. Shallow marine and coastal terrestrial climate anomalies appear to be out of phase after the Early Holocene warm period, and show complex regional patterns, but an overall trend of cooling in the terrestrial records. A Mid to Late Holocene warm period is present in many East Antarctic lake and shallow coastal marine records. Although there are some differences in the regional timing of this warm period, it typically occurs somewhere between 4.7 and 1 ka BP, which overlaps with a similar optimum found in Antarctic Peninsula terrestrial records. The differences in the timing of these sometimes abrupt warm events in different records and regions points to a number of mechanisms that we have yet to identify. Nearly all records show a neoglacial cooling from 2 ka BP onwards. There is no evidence along the East Antarctic coastline for an equivalent to the Northern Hemisphere Medieval Warm Period and there is only weak circumstantial evidence in a few places for a cool event crudely equivalent in time to the Northern Hemisphere's Little Ice Age. There is a need for well-dated, high resolution climate records in coastal East Antarctica and particularly in Terre Adélie, Dronning Maud Land and Enderby Land to fully understand the regional climate anomalies, the disparity between marine and terrestrial records, and to determine the significance of the heterogeneous temperature trends being measured in the Antarctic today.