Effingham Inlet Research Articles

The complete genome sequences of Thioglobus autotrophicus strains EF2 and EF3, isolated from an oxycline in Effingham Inlet, British Columbia.

Here we provide the complete genome sequences of two chemoautotrophic isolates from the Thioglobaceae family of marine gamma-proteobacteria. The genomes were obtained from pure cultures that were initially isolated from Effingham Inlet in 2013 and revived from freezer stocks for whole genome sequencing in 2023.

Bacterial and archaeal lipids trace chemo(auto)trophy along the redoxcline in Vancouver Island fjords.

Marine oxygen minimum zones play a crucial role in the global oceanic carbon, nitrogen, and sulfur cycles as they harbor microbial communities that are adapted to the water column chemistry and redox zonation, and in turn control the water column chemistry and greenhouse gas release. These micro-organisms have metabolisms that rely on terminal electron acceptors other than O2 and often benefit from syntrophic relationships (metabolic coupling). Here, we study chemo(auto)trophy along the redoxcline in two stratified fjords on Vancouver Island (Canada) using bacterial bacteriohopanepolyols and archaeal ether lipids. We analyze the distribution of these lipid classes in suspended particulate matter (SPM) to trace ammonia oxidation, anaerobic ammonium oxidation (anammox), sulfate reduction/sulfur oxidation, methanogenesis, and methane oxidation, and investigate ecological niches to evaluate potential links between their respective bacterial and archaeal sources. Our results show an unparalleled BHP and ether lipid structural diversity that allows tracing the major redox-driven metabolic processes at the time of sampling: Both fjords are dominated by archaeal ammonia oxidation and anammox; sulfate-reducing bacteria may be present in Deer Bay, but absent from Effingham Inlet; methanogenic Euryarchaeota and archaeal and bacterial methanotrophs are detectable at low abundance. Correlation analysis reveals distinct biomarker clusters that provide constraints on the biogeochemical niches of some orphan BHP and ether lipids such as in situ-produced adenosyl-BHPs or unsaturated archaeols.

Buoyancy‐driven coastal current blocks ventilation of an anoxic fjord on the Pacific coast of Canada

AbstractShallow sills restrict the ventilation of deep coastal fjords. Dense oceanic water seaward of the sill and lower density water within the receiving basin are generally required for oxygenated water to cross the sill and descend deep into the fjord. Here we use concurrent 10 year time series from current meters in the fjord and on the continental shelf to examine ventilation of the 120 m deep, anoxic inner basin of Effingham Inlet on the west coast of Vancouver Island. Whereas density currents traverse the 40 m deep sill and flow into the inner basin at mid‐depth at quasi‐fortnightly tidal intervals, only five current intrusions descended to the bottom of the basin over the decade‐long measurement period. The deep intrusions had a mean (±SD) return interval of 1.75 (±1.33) years and induced bottom‐water changes that persisted for 1–2 months. We show that, in addition to conditions within the inlet, deep ventilation of the inner basin is dependent on a coordinated sequence of external processes: (1) the onset of upwelling winds along the outer coast; (2) reversal of the buoyancy‐driven coastal current that normally flows poleward over the inner shelf off Vancouver Island; and (3) reversal of the estuarine circulation in the channel connecting the inlet to the ocean. As the observed ventilation intervals are short compared to the decadal intervals derived from the spacing of “homogenites” (sedimentation sequences disrupted by intruding bottom currents), the use of homogenites as proxies for past upwelling conditions in the northeast Pacific may need to be reexamined.

High resolution dinoflagellate cyst record of environmental change in Effingham Inlet (British Columbia, Canada) over the last millennium

We present a high resolution sedimentary record of dinoflagellate cysts spanning the last ~900years recovered from Effingham Inlet, a glacial fjord on the west coast of Vancouver Island, Canada. The combination of seasonal coastal upwelling supporting high levels of marine primary productivity in surface waters, together with restricted bottom water circulation in the silled fjord, fosters the preservation of laminated sediments in the inner basin of Effingham Inlet. Geochemical data are used to assess the sedimentary facies of the core, which is composed primarily of laminated units (50.2%) occasionally interrupted by “seismites” (39.5%) and homogenous units (10.2%). The chronology of the ~2m-long core is based on varve counting and fifteen 14C dates, and is anchored by a seismite previously dated at AD 1946.The dinoflagellate cyst assemblages are diverse (total of 47 taxa), abundant (average concentrations of 102,900cystg−1 of dry sediment), and characterized by a proportionally equal contribution of autotrophic and heterotrophic cyst taxa in most samples. Overall, cyst assemblages are characterized by Operculodinium centrocarpum (36.2%) accompanied by Brigantedinium spp. (18.0%) and Dubridinium spp. (6.6%). Multivariate analyses are used to extract the dominant patterns of variability in autotrophic and heterotrophic dinoflagellate cyst assemblages separately, and help in identifying the temperature and primary productivity gradients encoded in the cyst sedimentary record in this particular estuary.Specific intervals identified in the dinoflagellate cyst record are interpreted to represent the local expression of the “Medieval Climate Anomaly” (from the base of the record, ~AD 1090 to 1230), the “Little Ice Age” (~AD 1230 to late 19th century) and warming in the second half of the 20th century. The timing of these intervals are consistent with the regional paleoclimate and help constrain past climatic and oceanographic variability on the west coast of Vancouver Island. The origin of homogenous units in the sedimentary record of Effingham Inlet and paleoseismicity in the region are also discussed.

Slipstream: an early Holocene slump and turbidite record from the frontal ridge of the Cascadia accretionary wedge off western Canada and paleoseismic implications

Slipstream Slump, a well-preserved 3 km wide sedimentary failure from the frontal ridge of the Cascadia accretionary wedge 85 km off Vancouver Island, Canada, was sampled during Canadian Coast Guard Ship (CCGS) John P. Tully cruise 2008007PGC along a transect of five piston cores. Shipboard sediment analysis and physical property logging revealed 12 turbidites interbedded with thick hemipelagic sediments overlying the slumped glacial diamict. Despite the different sedimentary setting, atop the abyssal plain fan, this record is similar in number and age to the sequence of turbidites sampled farther to the south from channel systems along the Cascadia Subduction Zone, with no extra turbidites present in this local record. Given the regional physiographic and tectonic setting, megathrust earthquake shaking is the most likely trigger for both the initial slumping and subsequent turbidity currents, with sediments sourced exclusively from the exposed slump face of the frontal ridge. Planktonic foraminifera picked from the resedimented diamict of the underlying main slump have a disordered cluster of 14C ages between 12.8 and 14.5 ka BP. For the post-slump stratigraphy, an event-free depth scale is defined by removing the turbidite sediment intervals and using the hemipelagic sediments. Nine 14C dates from the most foraminifera-rich intervals define a nearly constant hemipelagic sedimentation rate of 0.021 cm/year. The combined age model is defined using only planktonic foraminiferal dates and Bayesian analysis with a Poisson-process sedimentation model. The age model of ongoing hemipelagic sedimentation is strengthened by physical property correlations from Slipstream events to the turbidites for the Barkley Canyon site 40 km south. Additional modelling addressed the possibilities of seabed erosion or loss and basal erosion beneath turbidites. Neither of these approaches achieves a modern seabed age when applying the commonly used regional marine 14C reservoir age of 800 years (marine reservoir correction ΔR = 400 years). Rather, the top of the core appears to be 400 years in the future. A younger marine reservoir age of 400 years (ΔR = 0 years) brings the top to the present and produces better correlations with the nearby Effingham Inlet paleo-earthquake chronology based only on terrestrial carbon requiring no reservoir correction. The high-resolution dating and facies analysis of Slipstream Slump in this isolated slope basin setting demonstrates that this is also a useful type of sedimentary target for sampling the paleoseismic record in addition to the more studied turbidites from submarine canyon and channel systems. The first 10 turbidites at Slipstream Slump were deposited between 10.8 and 6.6 ka BP, after which the system became sediment starved and only two more turbidites were deposited. The recurrence interval for the inferred frequent early Holocene megathrust earthquakes is 460 ± 140 years, compatible with other estimates of paleoseismic megathrust earthquake occurrence rates along the subduction zone.

A new high-resolution radiocarbon Bayesian age model of the Holocene and Late Pleistocene from core MD02-2494 and others, Effingham Inlet, British Columbia, Canada; with an application to the paleoseismic event chronology of the Cascadia Subduction Zone

Annually laminated sediments from the anoxic inner basin of Effingham Inlet, Pacific coast of Vancouver Island, British Columbia, Canada, yield a high-resolution 42 m paleoenvironmental record, from the present to about 14 ka 14C BP (17 ka cal BP). A new age model, based on 68 radiocarbon dates from twigs and small plant material, from the 40 m core MD02-2494 and 2 m freeze cores from the surface, is anchored by the Mazama Ash and varve counting. A Poisson-process sedimentation model is used, applying a new method to determine the Poisson k value, giving a realistic age model compatible with the multi-proxy core data. Twenty-one “seismites”, which are lithofacies in the Effingham cores that may be representative of seismically triggered mass-wasting events, are identified and dated precisely, then compared with the chronology of the deep-sea turbidite record farther south in the Cascadia Subduction Zone (CSZ), to determine if regional sediment disturbances can be identified. With 16 proposed correlations, Effingham seismite ages are 169 ± 206 years older than turbidite ages estimated largely by radiocarbon analysis of foraminifera in hemipelagic deposits.

Influence of the Pacific Decadal Oscillation, El Niño-Southern Oscillation and solar forcing on climate and primary productivity changes in the northeast Pacific

Evidence of 11-year Schwabe solar sunspot cycles, El Niño-Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO) were detected in an annual record of diatomaceous laminated sediments from anoxic Effingham Inlet, Vancouver Island, British Columbia. Radiometric dating and counting of annual varves dates the sediments from AD 1947–1993. Intact sediment slabs were X-rayed for sediment structure (lamina thickness and composition based on gray-scale), and subsamples were examined for diatom abundances and for grain size. Wavelet analysis reveals the presence of ∼2–3, ∼4.5, ∼7 and ∼9–12-year cycles in the diatom record and an ∼11–13 year record in the sedimentary varve thickness record. These cycle lengths suggest that both ENSO and the sunspot cycle had an influence on primary productivity and sedimentation patterns. Sediment grain size could not be correlated to the sunspot cycle although a peak in the grain size data centered around the mid-1970s may be related to the 1976–1977 Pacific climate shift, which occurred when the PDO index shifted from negative (cool conditions) to positive (warm conditions). Additional evidence of the PDO regime shift is found in wavelet and cross-wavelet results for Skeletonema costatum, a weakly silicified variant of S. costatum, annual precipitation and April to June precipitation. Higher spring (April/May) values of the North Pacific High pressure index during sunspot minima suggest that during this time, increased cloud cover and concomitant suppression of the Aleutian Low (AL) pressure system led to strengthened coastal upwelling and enhanced diatom production earlier in the year. These results suggest that the 11-year solar cycle, amplified by cloud cover and upwelling changes, as well as ENSO, exert significant influence on marine primary productivity in the northeast Pacific. The expression of these cyclic phenomena in the sedimentary record were in turn modulated by the phase of PDO, as indicated by the change in period of ENSO and suppression of the solar signal in the record after the 1976–1977 regime shift.

Annual record of particle fluxes, geochemistry and diatoms in Effingham Inlet, British Columbia, Canada, and the impact of the 1999 La Niña event

Sediment traps were deployed inside the anoxic inner basin of Effingham Inlet and at the oxygenated mouth of the inlet from May 1999 to September 2000 in a pilot study to determine the annual depositional cycle and impact of the 1999 La Niña event within a western Canadian inlet facing the open Pacific Ocean. Total mass flux, geochemical parameters (carbon, nitrogen, opal, major and minor element contents, and stable isotope ratios) and diatom assemblages were determined and compared with meteorological and oceanographic data. Deposition was seasonal, with coarser grained terrestrial components and benthic diatoms settling in the autumn and winter, coincident with the rainy season. Marine sedimentary components and abundant pelagic diatoms were coincident with coastal upwelling in the spring and summer. Despite the seasonal differences in deposition, the typical temperate-zone Thalassiosira – Skeletonema – Chaetoceros bloom succession was muted. A July 1999 total mass flux peak and an increase in biogenous components coincided with a rare bottom-water oxygen renewal event in the inlet. Likewise, there were cooler-than-average sea surface temperatures (SSTs) just outside the inlet, and unusually high abundances of a previously undescribed cool-water marine diatom ( Fragilariopsis pacifica sp. nov.) within the inlet. Each of these occurrences likely reflects a response to the strong La Niña that followed the year after the strongest-ever recorded El Niño event of 1997–1998. By the autumn of 1999, SSTs had returned to average, and F. pacifica had all but disappeared from the remaining trap record, indicating that oceanographic conditions had returned to normal. Oxygenation events were not witnessed in the inlet in the years before or after 1999, suggesting that a rare oceanographic and climatic event was captured by this sediment trap time series. The data from this record can therefore be used as a benchmark for identifying anomalous environmental conditions on this coast. ► Only sediment trap study done in a western Canadian inlet facing the open Pacific ► Deposition of settling particles is clearly seasonal. ► Deposition of settling particles is also influenced by the 1999 La Niña event. ► 1999 La Niña had a strong oceanographic and biological effect on the coast. ► Sediment trap data can be used as benchmarks recording anomalous climatic events.

Potential role of inorganic polyphosphate in the cycling of phosphorus within the hypoxic water column of Effingham Inlet, British Columbia

The upper basin of Effingham Inlet possesses permanently anoxic bottom waters, with a water column redox transition zone typically occurring at least 40 m above the sediment‐water interface. During our sampling campaign in April and July 2007, this redox transition zone was associated with sharp peaks in a variety of parameters, including soluble reactive phosphorus (SRP) and total particulate phosphorus (TPP). Based on sequential extraction results, TPP maxima exhibited preferential accumulation of an operationally defined class of loosely adsorbed organic phosphorus (P), which may contain a substantial fraction of polyphosphate (poly‐P). This poly‐P may furthermore be involved in the redox‐dependent remobilization of SRP. For example, direct fluorometric analysis of poly‐P content revealed that particulate inorganic poly‐P was present at concentrations ranging from 1 to 9 nM P within and several meters above the TPP maximum. Below the depth of 1% oxygen saturation, however, particulate inorganic poly‐P was undetectable (<0.8 nM in situ). Assuming this concentration profile reflects the remineralization of inorganic poly‐P to SRP across the redox transition, inorganic poly‐P degradation accounted for as much as 4 ± 3% (average ± standard deviation) to 9 ± 8% of the vertical turbulent diffusive SRP flux. This finding is a conservative estimate due in part to sample storage effects associated with our analysis of poly‐P content. By comparison, iron‐linked P cycling accounted for at most 65 ± 33% of the diffusive SRP flux, leaving ∼25% unaccounted for. Thus, while redox‐sensitive poly‐P remineralization in Effingham Inlet appears modest based on our direct conservative estimate, it may be higher from a mass balance viewpoint. Poly‐P cycling may therefore be an overlooked mechanism for the redox‐sensitive cycling of P in some hypoxic/anoxic boundaries, especially iron‐poor marine oxygen minimum zones.

Dinoflagellate cyst-based reconstructions of mid to late Holocene winter sea-surface temperature and productivity from an anoxic fjord in the NE Pacific Ocean

Published contemporary dinoflagellate distributional data from the NE Pacific margin and estuarine environments ( n = 136) were re-analyzed using Canonical Correspondence Analysis (CCA) and partial Canonical Correspondence Analysis (pCCA). These analyses illustrated the dominant controls of winter temperature and productivity on the distribution of dinoflagellate cysts in this region. Dinoflagellate cyst-based predictive models for winter temperature and productivity were developed from the contemporary distributional data using the modern analogue technique and applied to subfossil data from two mid to late Holocene (∼5500 calendar years before present–present) cores; TUL99B03 and TUL99B11, collected from Effingham Inlet, a 15 km long anoxic fjord located on the southwest coast of Vancouver Island that directly opens to the Pacific Ocean through Barkley Sound. Sedimentation within these basins largely comprises annually deposited laminated couplets, each made up of a winter deposited terrigenous layer and spring to fall deposited diatomaceous layer. The Effingham Inlet dinoflagellate cyst record provides evidence of a mid-Holocene gradual decline in winter SST, ending with the initiation of neoglacial advances in the region by ∼3500 cal BP. A reconstructed Late Holocene increase in winter SST was initiated by a weakening of the California Current, which would have resulted in a warmer central gyre and more El Niño-like conditions.

Marine Dissolved Organic Phosphorus Composition: Insights from Samples Recovered Using Combined Electrodialysis/Reverse Osmosis

The dominant phosphorus compound classes were characterized in marine samples using a new, high recovery method for isolating and concentrating bulk dissolved organic matter (DOM) called combined electrodialysis + reverse osmosis (ED/RO). In contrast to earlier studies that use ultrafiltration (UF) to recover only the high molecular weight DOM, ED/RO is capable of isolating both low molecular weight (LMW) and high molecular weight (HMW) DOM. Samples were collected from a broad range of marine environments: along a transect incorporating coastal and offshore waters off the Southeastern United States, in Effingham Inlet, a Pacific fjord located on Vancouver Island, British Columbia and in the Amundsen Sea, Antarctica. Results from phosphorus nuclear magnetic resonance (31P NMR) analysis reveal a similar abundance of P compound classes among samples, phosphate esters (80–85%), phosphonates (5–10%) and polyphosphates (8–13%). These samples contain significantly higher proportions of polyphosphate P and P esters and lower proportions of phosphonates than measured in previous studies using the UF method. The much higher levels of polyphosphate detected in our samples suggests that polyphosphate is present mainly in the LMW dissolved matter fraction. Polyphosphates in dissolved matter may be present as (or derived from) dissolved nucleotides or organismal polyphosphate bodies, or both. Low molecular weight P esters are possibly composed of phosphoamino acids and small carbohydrates, like simple sugar phosphates and/or dissolved nucleotides. Phosphonates in DOM are more prevalent as HMW phosphonate compounds, which suggests that LMW phosphonates are more readily utilized in marine ecosystems. Overall, the investigation of DOM across a size spectrum that includes both the HMW and the LMW fractions reveals a new picture of phosphorus distribution, cycling and bioavailability.

Geochemical and diatom signatures of bottom water renewal events in Effingham Inlet, British Columbia (Canada)

Sediments from Effingham Inlet, Vancouver Island, British Columbia hold a valuable high-resolution Holocene record of paleoclimatic and paleoceanographic conditions in the northeast Pacific Ocean. Accurate interpretation of this record requires that the depositional environment be well understood. In order to assess deposition within the fjord over the last 1500 years, two cores, a Soutar box core and a Kasten core, were analyzed for fossil diatoms, and biogeochemical properties. The cores contain varved sequences intercalated with homogeneous mud layers and a seismite. We show that homogeneous mud units related to periods of bottom water renewal are geochemically distinct from the seismite and that these bottom renewal events are favored when brackish rather than marine surface water conditions are present. The seismite, deposited in AD 1946, has lower opal and higher organic carbon concentrations and higher organic carbon: nitrogen ratios reflecting greater terrestrial material input. In contrast, homogeneous mud units are marked by a lower organic C/N and more isotopically heavy δ 13C values, suggesting a stronger marine influence. Major metals and trace element data also confirm that the source material of these units differs from that of the AD 1946 seismite. Fossil diatom assemblages within the homogeneous mud units are characterized by a decreased abundance of typical marine spring bloom taxa ( Skeletonema costatum, Chaetoceros spp., Thalassiosira spp.) coupled with an increased abundance of the brackish-water taxon Cyclotella choctawhatcheeana. Reduced surface salinity enhances stratification of the water column which, in turn, favors an intensified two-layer estuarine exchange across the shallow sills and associated bottom water renewal. The homogeneous mud units are produced through transport of sediment into the fjord coupled with a reworking of the upper layers of the sediment column. Therefore, these units represent a recorder of past changes in regional oceanography and climate.

Geochemical reconstruction of Pacific decadal variability from the eastern North Pacific during the HoloceneThis article is one of a series of papers published in this Special Issue on the themePolar Climate Stability Network.

Determining climate variations over the Holocene requires high-resolution records with well-developed age models. A 40 m long marine sediment core raised from Effingham Inlet, an anoxic fjord on the west coast of Vancouver Island, British Columbia, Canada, yields such a record. Forty six14C accelerator mass spectrometry (AMS) dates determined from terrestrial plant material form the age model. Downcore sampling at both 5 cm (20 year) and 1.5 cm (7 year) resolution indicates that high-frequency oceanographic variability has prevailed at this site over the last 10 000 years. Spectral analysis of wt.% opal, a proxy for diatom productivity in the basin, reveals the bidecadal and pentadecadal periods of the Pacific decadal oscillation (PDO) – North Pacific index (NPI) that are related to changes in the strength of the Aleutian Low. Coherence analysis between the Effingham Inlet data and δ18O records from Jellybean Lake (a high elevation site in southwest Yukon) indicates regional coherence at periods of 45, 70, and 510 years between productivity in Effingham Inlet and changes in the Aleutian Low strength. Over the entire Holocene, the strength of decadal variability has changed. Both 20- and 50-year periods are present to some degree in the early Holocene, and only the 50 year period is evident in the late Holocene. These data imply that regime shifts would have been more frequent in the early Holocene relative to the last several thousand years.

Determining the post-glacial evolution of a northeast Pacific coastal fjord using a multiproxy geochemical approachThis article is one of a series of papers published in this Special Issue on the theme Polar Climate Stability Network.

A 40.32 m piston core recovered from Effingham Inlet, on the west coast of Vancouver Island, provides the basis for a high-resolution geochemical study of the last deglaciation and the Holocene. Glacial retreat, basin isolation, sea-level rise, and productivity variations are determined using proxies for sediment composition (K/Al, Fe/Al, Mg/Al), grain size (Ti/Al, Zr/Al), sedimentary redox conditions (Mo/Al, U/Al), and productivity (wt.% organic carbon, wt.% opal). As local ice retreated and marine waters inundated the basin, coarse-grained glacimarine sediments were replaced by finer grained, laminated, opal-rich sediments. During meltwater pulse-1a, the dominance of local crustal rise over eustatic sea-level rise resulted in the progressive restriction of ocean circulation in Effingham Inlet and the formation of a temporary freshwater lake. The transition into stable Holocene conditions was initiated at ∼12 700 BP, which corresponds to the onset of the Younger Dryas, as identified by the Greenland Ice core Project (GRIP) ice core δ18O record and was completed by 10 700 BP, ∼800 years after the GRIP ice core record stabilized. Holocene Mo/Al and U/Al ratios range between 12–35 (×104) and 1–3.4 (×104), respectively, indicating that although large-amplitude, high-frequency fluctuations occur, the sediments of Effingham Inlet inner basin have remained organic rich and oxygen depleted for the entire Holocene period. The combination of anoxic bottom waters and a Holocene sedimentation rate of 217 cm/ka have preserved a high-resolution record of environmental change in the northeast Pacific over the last 11 000 years.

Postglacial evolution of a Pacific coastal fjord in British Columbia, Canada: interactions of sea-level change, crustal response, and environmental fluctuations — results from MONA core MD02-2494This article is one of a series of papers published in this Special Issue on the theme Polar Climate Stability Network.

The sedimentary record in a 40.9 m giant (Calypso) piston core (MD02-2494) raised from the inner basin within Effingham Inlet, British Columbia, Canada, during the 2002 Marges Ouest Nord Américaines (MONA) campaign, spans from 14 360 14C years BP (17 300 calibrated calendar (cal.) years BP) to about nine centuries before present. The core archives changes in sedimentation and sea level immediately following deglaciation of the Late Wisconsin Fraser Glaciation, which peaked about 15 000 14C years BP. The presence of the Mazama Ash in the core anchors a detailed chronology based on 49 radiocarbon dates and seven Pleistocene paleomagnetic secular variation correlations. Diatom assemblages identify a marine–freshwater–marine transition in the basin, which occurred 11 630 14C years BP (13 500 cal. years BP). At this time, a bedrock sill, presently at 46 m depth, was briefly exposed as sea level fell and then rose again during isostatic crustal adjustments. These data constrain a new sea-level curve for the outer coast of Vancouver Island covering the past 12 000 14C years BP (14 000 cal. years BP), providing new information on the nature of deglaciation along the west coast of Canada and informing interpretations of regional paleoceanographic records and mantle viscosity models.

Siliceous microfossil record of late Holocene oceanography and climate along the west coast of Vancouver Island, British Columbia (Canada)

Diatoms, silicoflagellates, and biogenic silica (BSi) were analyzed from two piston cores recovered from Effingham Inlet, British Columbia. Relatively productive marine conditions from 4850 to 4000 cal yr BP were followed by a transition to the modern ocean–climate regime marked by a decreased siliceous microfossil production since 2800 cal yr BP. This change in the northeast Pacific climate was characterized by an apparent cooling associated with higher rainfall and lower light levels. The reduced abundance of most spring–summer bloom diatom taxa ( Skeletonema–Thalassiosira–Chaetoceros) was coupled with a decreased abundance of diatoms normally associated with incursions of offshore water into coastal inlets. This pattern reflected a weaker summer upwelling along Vancouver Island associated with the insolation-related increase in the strength of the Aleutian Low and a weakened North Pacific High. After ca. 2800 cal yr BP, diatom assemblages also indicated more frequent periods of relatively low spring–summer surface water salinity and a disruption of the typical bloom sequence, indicative of increased climatic variability. A period of warmer and drier climate conditions and possibly increased coastal upwelling offshore occurred ca. 1450–1050 cal yr BP. The most recent 500 yr are marked by reduced diatom production and the appearance of three distinct diatom biomarkers in the stratigraphic record ( Rhizosolenia setigera ca. AD 1940; Minidiscus chilensis ca. AD 1860; Thalassionema nitzschioides morphotype A, ca. AD 1550). The oceanographic changes recorded in Effingham Inlet are correlative with other marine and terrestrial paleoenvironmental records in the northeast Pacific Ocean.

A critical look at iron paleoredox proxies: New insights from modern euxinic marine basins

Enrichments in reactive iron occur under euxinic marine conditions, that is, where dissolved sulfide is present in the water column. These enrichments result primarily from the export of remobilized iron from the oxic shelf, which is scavenged from the euxinic water column during syngenetic pyrite formation and deposited in the underlying sediments. Strongly elevated ratios of highly reactive iron to total iron (Fe HR/Fe T) and total iron to aluminum (Fe T/Al) and high degrees of pyritization (DOP) are each products of this enrichment process. These paleoredox proxies are among the most faithful recorders of ancient euxinia. Contrary to previous arguments, iron enrichment is decoupled from biogenic sediment inputs, but it does appear to be a uniquely euxinic phenomenon. In other words, we can rule out a major contribution from preferential physical transport of Fe HR-rich detrital sediment to the deep basin, which could also operate under oxic conditions. Furthermore, enrichment via the shuttling of iron remobilized from oxic shelves appears to be limited by inefficient transport and trapping processes in deep oxic basins. Elevated Fe T/Al ratios in the euxinic sediments also cannot be a product of internal enhancement of the reactivity of the detrital iron pool without net Fe HR addition. These conclusions are supported by observations in the modern Black Sea, Orca Basin, and Effingham Inlet. Fe T/Al ratios are unambiguous recorders of paleoredox even in sediments that have experienced high degrees of metamorphic alteration. However, this study suggests that high siliciclastic accumulation rates can swamp the enrichment mechanism, resulting in only intermediate DOP values for euxinic sediments and Fe T/Al ratios that mimic the oxic shelf. Such dilution effects are well expressed in Black Sea basinal turbidites and rapidly accumulating muds on euxinic basin margins. Under conditions of persistent euxinia, varying extents of Fe HR enrichment can illuminate spatial and temporal gradients in siliciclastic sedimentation. The magnitude of enrichment is a function of the source (shelf) to sink (ocean basin) areal ratio, suggesting that iron proxies can also record ocean-scale paleoenvironmental properties through muted enrichments at times of very widespread euxinia. For the first time, manganese data are interpreted in light of the redox shuttle model. As for the iron data, the Black Sea, Orca Basin, and Effingham Inlet show enrichments in total manganese in the deep euxinic basin, suggesting export from the suboxic porewaters of the oxic shelf and scavenging and burial in the basin. The Black Sea data reveal iron and manganese enrichment across the broad, deep euxinic basin, suggesting efficient lateral transport and deep-water mixing tied to the physical properties of the water column.

Polyphosphates as a source of enhanced P fluxes in marine sediments overlain by anoxic waters: Evidence from 31P NMR.

Sedimentary phosphorus (P) composition was investigated in Effingham Inlet, a fjord located on the west coast of Vancouver Island in Barkley Sound. Solid-state 31P nuclear magnetic resonance (NMR) spectroscopy was applied to demineralized sediment samples from sites overlain by oxic and anoxic bottom waters. The two sites were similar in terms of key diagenetic parameters, including the mass accumulation rate, integrated sulfate reduction rate, and bulk sediment organic carbon content. In contrast, P benthic fluxes were much higher at the anoxic site. 31P NMR results show that P esters and phosphonates are the major organic P species present at the surface and at depth in sediments at both sites. Polyphosphates were only found in the surface sediment of the site overlain by oxic waters. The varying stability of polyphosphates in microorganisms under different redox conditions may, in part, explain their distribution as well as differences in P flux between the two sites.

Late Holocene paleofish populations in Effingham Inlet, British Columbia, Canada

Paleontological studies of fish remains in laminated sediments provide a proxy relationship between fish populations and ocean climate. This study examines climate variability from approximately 500 y B.P. to 4000 y B.P. as recorded in fish remain abundances (primarily scales) collected from laminated sediments within Effingham Inlet on the west coast of Vancouver Island, British Columbia. The study also discusses technical issues involving fish remains from laminated sediments, including sampling resolution, sediment volume, identification of remains and appropriate abundance considerations. The dominant species in the assemblage include Northern anchovy and Pacific herring, with lesser percentage-abundances from rockfish, hake, elasmobranches and surfperch. The data indicate that Northern anchovy experienced a shift in scale deposition abundance at approximately 2800 y B.P. with not only a greater total abundance but also a greater consistency of deposition with time. Pacific herring underwent cyclical deposition that changed little through time. Statistical analysis reveals that none of these species is directly responding to climatic signals as indicated in the lithological and palynological record, but that this could have been partially due to the sampling resolution of the piston core. Analysis indicates a lack of correlation between the two dominant species, as might be expected on the basis of their opposing lifestyle strategies with respect to sea surface temperatures. With appropriate sampling strategies, paleohistorical fish remains from laminated sediments reflect changes in population structure and behaviour for some species, illustrate basic secondary trophic information, and provide potential clues to basin-scale oceanographic/climatological variability.

Modern to Late Holocene deposition in an anoxic fjord on the west coast of Canada: Implications for regional oceanography, climate and paleoseismic history

Laminated sediments preserved in the anoxic inner basin of Effingham Inlet on the Pacific coast of Vancouver Island, British Columbia, Canada, yield a high-resolution sediment deposition record spanning about 6000 yr. The varying thickness of diatom/terrigenous mud varves in sediment cores from the basin can be interpreted in terms of annual changes in surface productivity and freshwater input within the inlet. Similarly, the occurrence of unlaminated mud units (homogenites) intercalated amongst the laminated sediments can be interpreted in terms of oceanic and climatic changes. These units appear to be associated with coastal upwelling events that result infrequently in highly oxygenated oceanic water penetrating to the bottom of the inner and outer basins of the inlet. The sedimentary record also contains massive and graded mud units considered to arise from debris flows and turbidity currents, some of which were probably initiated by seismic events, including a major event about 4500 14C yr BP which may be earthquake related. A total of seventeen oceanographic surveys of the inlet beginning in 1995 characterize the modern seasonal coastal upwelling regime and a unique bottom water oxygenation event which was recorded in January 1999, following a rapid transition from the strong El Niño event of 1997–98 to the moderate La Niña event of 1998–99. Circum-Pacific evidence suggests that a “regime shift” from warm to cold conditions occurred in the central northeast Pacific in the late 1990s, indicating that the coastal ocean processes influencing Effingham Inlet sedimentation are likely modified by climate-scale ocean variability.