The Role of Submerged Aquatic Vegetation in Structuring the Nearshore Fish Community Within an Estuary of the Southern Gulf of St. Lawrence

Artificial fertilizers are contributing to the replacement of eelgrass (Zostera marina) by sea lettuce (Ulva lactuca) in estuaries of Prince Edward Island (PEI), Canada. In this study, we found that the nearshore fish community differed between areas dominated by these two vegetations within an estuary in every month sampled (April–August). Adult northern pipefish (Syngnathus fuscus), threespine stickleback (Gasterosteus aculeatus), blackspotted stickleback (Gasterosteus wheatlandi), and Atlantic silverside (Menidia menidia) were most strongly associated with eelgrass, while mummichog (Fundulus heteroclitus), ninespine stickleback (Pungitius pungitius), and American eel (Anguilla rostrata) were often more numerous in sea lettuce. Sea lettuce stations tended to have more young-of-the-year mummichog, fourspine stickleback (Apeltes quadracus), and Gasterosteus sp. than eelgrass stations but fewer young-of-the-year northern pipefish and Atlantic silverside. Fish richness and abundance were significantly lower in the sea lettuce than eelgrass habitat during August when benthic hypoxia occurred. We conclude that the loss of eelgrass from PEI estuaries will result in significant declines in fish biodiversity.     

Sources,sinks and distribution of organic carbon in the St. Lawrence Estuary,Canada

Carbon isotope ratio analysis of particulate, planktonic, and sedimentary organic carbon and dissolved inorganic carbon has been used to study the sources and sinks of the organic carbon in the St. Lawrence Estuary and Gulf of St. Lawrence, Canada. Particulate organic carbon (POC) isotope ratios in the upper St. Lawrence Estuary are uniform and indistinguishable from those of POC in the St. Lawrence River and of planktonic organic carbon in both areas. The abundance of freshwater diatoms in the upper Estuary suggests that upper Estuary POC is predominantly “fresh” organic matter of riverborne origin. Upper Estuary POC is isotopically different from POC in the lower St. Lawrence Estuary and Gaspé regions, but is not different from POC from the surface waters of the open Gulf of St. Lawrence. The isotopic composition of planktonic organic carbon mirrors that of the POC, indicating that the POC in the lower Estuary and Gulf is also “fresh” organic matter. Since the lower Estuary POC forms an isotopic barrier between the upper Estuary POC and the Gulf of St. Lawrence POC, there appears to be little mixing of POC between these three reservoirs. Therefore POC in the lower Estuary and Gulf is most likely both produced and deposited (or degraded) in situ.An examination of carbon isotope ratio differences between the planktonic and dissolved inorganic carbon reservoirs shows that this difference varies significantly and somewhat unpredictably between sectors of the study area. Interpretation of environmental carbon isotope data on the basis of an assumed, constant fractionation factor may be subject to large errors. Direct measurement of both reservoirs is obviously preferable.     

Seasonal and annual variations in the organic matter contributed by the St Lawrence River to the Gulf of St. Lawrence

The St. Lawrence River discharges a substantial volume of water (405 km³/a) containing suspended (SPM; 3.42 × 10⁶t) and dissolved (68.0 × 10⁶t) materials to the Gulf of St. Lawrence. The total load contains organic carbon in paniculate (POC; 3–14% of SPM), and dissolved (DOC; 3.76 ± 0.63 mg/l) form. The concentration of POC (and particulate organic nitrogen) is positively correlated with discharge (increased during the spring flood and the fall enhancement of flow), but concentration of DOC is not so simply related to discharge. In consequence, the total organic carbon (POC + DOC) load is relatively invariant, and increased annually by only 2–3% despite a progressive increase of 8% in discharge over the years of this study. Seasonal differences in the composition of the particulate organic matter (POM) are interpreted as reflecting dominant contributions from within-river production in summer and from terrestrial sources in spring and fall. In years when the annual discharge was greater than average, a higher proportion of the POM was terrigenous. The organic matter in surface sediments of the estuary to which the river discharges is predominantly of terrestrial provenance.     

Humic acids from particulate organic matter in the Saguenay Fjord and the St. Lawrence Estuary investigated by advanced solid-state NMR

Detailed structural information on two humic acids extracted from two sinking particulate matter samples at a water depth of 20 m in the Saguenay Fjord (F-20-HA) and the St. Lawrence Estuary (E-20-HA) (Canada), was obtained by advanced solid-state NMR. Spectral-editing analyses provided numerous structural details rarely reported in geochemical studies. The NMR data account almost quantitatively for the elemental compositions. The two humic acids were found to be quite similar, consisting of four main structural components: peptides (ca. 39 ± 3% vs. 34 ± 3% of all C for E-20-HA and F-20-HA, respectively); aliphatic chains, 14-20 carbons long (ca. 25 ± 5% vs. 17 ± 5% of all C); aromatic structures (ca. 17 ± 2% vs. 26 ± 2% of all C); and sugar rings (14 ± 2% vs. 15 ± 2% of all C). Peptides were identified by ¹³C{¹⁴N} SPIDER NMR, which selects signals of carbons bonded to nitrogen, and by dipolar DEPT, which selects CH-group signals, in particular the NCH band of peptides. The SPIDER spectra also indicate that heterocycles constitute a significant fraction of the aromatic structures. The aliphatic (CH₂)_n chains, which are highly mobile, contain at least one double bond per two chains and end in methyl groups. ¹H spin diffusion NMR experiments showed that these mobile aliphatic chains are in close (<10 nm) proximity to the other structural components. A major bacterial contribution to these two samples could explain why the samples, which have different dominant organic matter sources (terrestrial vs. marine), are similar to each other as well as to degraded algae and particles from other waters. The NMR data suggest structures containing mobile lipids in close proximity to peptides and carbohydrates (e.g., peptidoglycan) as found in bacterial cell walls. Measured yields of muramic acid and d-amino acids confirmed the presence of bacterial cell wall components in the studied samples.     

Decadal Changes in Water Quality and Net Productivity of a Shallow Danish Estuary Following Significant Nutrient Reductions

We utilized an extensive data set (1977–2013) from a water quality monitoring program to investigate the recovery of a Danish estuary following large reductions in total phosphorus (TP) and total nitrogen (TN) loading. Monthly rates of net transport and biogeochemical transformation of dissolved inorganic nitrogen (DIN) and phosphorus (DIP) were computed in two basins of the estuary using a box model approach, and oxygen-based rates of net ecosystem production (NEP) were determined. Since 1990, nutrient loading was reduced by 58 % for nitrogen and 80 % for phosphorus, causing significant decreases in DIN (60 %) and DIP (85 %) concentrations. Reductions in nutrient loadings and concentrations reduced annual chlorophyll levels by 50 % in the inner estuary and improved Secchi depth by approximately 1 m during the same period, particularly in the summer period. In the outer, deeper region of the estuary trends in water quality was less evident. Improvements in the inner estuary were strongly coupled to declines in DIN. Thresholds of DIN and DIP concentrations limiting phytoplankton growth indicated that both regions of the estuary were nitrogen limited. NEP rates indicated the development of more net autotrophic conditions over time that were likely associated with higher benthic primary production stimulated by improved light conditions. Box model computations revealed a modest reduction in summer net production of DIP over time, despite the persistence of elevated fluxes for several years after external loads were reduced. Since the mid-1990s, nutrient loading and transformation were stable while nutrient concentrations continued to decline and water quality improved in the inner estuary. The oligotrophication trajectory involved an initial fast transformation and modest retention of nutrients followed by a gradual decline in the rate of improvement towards a new stable condition.     

Response of Tidal Creek Fish Communities to Dredging and Coastal Development Pressures in a Shallow-Water Estuary

To investigate the effects of dredging and associated development pressures (i.e., shoreline armoring, developed land use) on fish, three sets of paired dredged and undredged tidal creeks were surveyed within Lynnhaven River, Virginia. Fish species diversity, community abundance, biomass, and size structure were compared among creeks and related to watershed, shoreline, and physicochemical characteristics. Mean fish community characteristics (e.g., abundance) were similar among creeks; however, species-specific analysis revealed subtle differences. Species biomass differed between dredged and undredged creeks, though species abundance was similar. Turbidity highly influenced differences in species abundance among creeks, while organic matter, dissolved oxygen, turbidity, and shoreline hardening may be influencing biomass patterns. The most recently dredged creek appeared to provide less suitable nursery habitat for some species than historically dredged creeks, suggesting initial adverse effects with eventual recovery. Protective measures, such as preservation of marshes, dredge depth, and time-of-year restrictions, may be moderating development and dredging pressures.     

Nekton Communities in Hawaiian Coastal Wetlands: The Distribution and Abundance of Introduced Fish Species

Nekton communities were sampled from 38 Hawaiian coastal wetlands from 2007 to 2009 using lift nets, seines, and throw nets in an attempt to increase our understanding of the nekton assemblages that utilize these poorly studied ecosystems. Nekton were dominated by exotic species, primarily poeciliids (Gambusia affinis, Poecilia spp.) and tilapia. These fish were present in 50–85% of wetlands sampled; densities were up to 15 times greater than native species. High densities of exotic fish were generally found in isolated wetlands with no connection to the ocean, were often the only nekton present, were positively correlated with surface water total dissolved nitrogen, and were negatively correlated with native species richness. Native species were present in wetlands with complete or partial connection to the ocean. Additional studies are needed to document exotic fish impacts on native fish and bird habitat and whether native fish communities can contribute to invasion resistance of coastal wetlands. Future wetland restoration should include exotic fish eradication, maintenance of hydrological connection to the ocean, or programs to prevent future introductions in order to create wetlands that support native-dominated nekton communities.     

Influence of the Laurentide Ice Sheet and relative sea‐level changes on sediment dynamics in the Estuary and Gulf of St. Lawrence since the last deglaciation

Physical properties, grain size, bulk mineralogy, elemental geochemistry and magnetic parameters of three sediment piston cores recovered in the Laurentian Channel from its head to its mouth were investigated to reconstruct changes in detrital sediment provenance and transport related to climate variability since the last deglaciation. The comparison of the detrital proxies indicates the succession of two sedimentary regimes in the Estuary and Gulf of St. Lawrence (EGSL) during the Holocene, which are associated with the melting history of the Laurentide Ice Sheet (LIS) and relative sea‐level changes. During the early Holocene (10–8.5 cal. ka BP), high sedimentation rates together with mineralogical, geochemical and magnetic signatures indicate that sedimentation in the EGSL was mainly controlled by meltwater discharges from the local retreat of the southeastern margin of the LIS on the Canadian Shield. At this time, sediment‐laden meltwater plumes caused the accumulation of fine‐grained sediments in the ice‐distal zones. Since the mid‐Holocene, postglacial movements of the continental crust, related to the withdrawal of the LIS (c. 6 cal. ka BP), have triggered significant variations in relative sea level (RSL) in the EGSL. The significant correlation between the RSL curves and the mineralogical, geochemical, magnetic and grain‐size data suggest that the RSL was the dominant force acting on the sedimentary dynamics of the EGSL during the mid‐to‐late Holocene. Beyond 6 cal. ka BP, characteristic mineralogical, geochemical, magnetic signatures and diffuse spectral reflectance data suggest that the Canadian Maritime Provinces and western Newfoundland coast are the primary sources for detrital sediments in the Gulf of St. Lawrence, with the Canadian Shield acting as a secondary source. Conversely, in the lower St. Lawrence Estuary, detrital sediments are mainly supplied by the Canadian Shield province. Finally, our results suggest that the modern sedimentation regime in the EGSL was established during the mid‐Holocene.     

Sedimentation cycle of a freshwater tidal flat in the St. Lawrence estuary

Cap-Tourmente tidal flat is located on the north shore of the St. Lawrence middle estuary, 50 km downstream from Quebec city, Canada. Seasonal variations in sedient accretion were studied during the period without ice from May to December, using horizontal plates in conjunction with vertical stakes. The sedimentological regime which is characterized by very rapid changes, can be divided into four periods. There are two periods of intense erosion in May and October–November; during these months, erosion is initiated by walking and beak probing of very large flocks of snow geese. During the summer, very rapid accretion occurs for approximately 100 days; during this period, the sedimentation rate is 2 mm per day in the lower section of the tidal marsh which is covered with vegetation. Among the numerous factors influencing the sedimentation cycle, the very gradual slope of the upper part of the flat (0.25%) seems to be one of the most important because it results in a very large area (550 m wide) which is protected from strong tidal currents. This latter area is covered with dense and high vegetation which provides an effective protection against erosion unitl the snow geese arrive in October and raze it in a few days. The presence of vegetation reduces the velocities of tidal currents, particularly during ebb and modifies their direction for both flood and ebb, orienting them perpendicularly to the main tidal flow.     

Physical processes controlling bacterial distribution and variability in the upper St. Lawrence estuary

The vertical structure of the water column and the spatial distribution and semidiurnal variability of bacteria were investigated at six stations in the upper St. Lawrence estuary. The σ₁ profiles indicate that the upper St. Lawrence is a partially mixed estuary. Stratification results from buoyancy input from the freshwater outflow of the St. Lawrence River, and its variability is controlled by tidal and, to a lesser extent, wind mixing. Calculations show that tidal mixing largely exceeds mixing caused by wind. Free and attached bacteria presented different patterns of spatial distribution and temporal variability. Free bacteria exhibited highest mean concentrations at the freshwater station (3.5–4.4 10⁶ml^?1) and lowest concentrations at the downstream stations (0.3–0.5 10⁶ml^?1); their numbers declined exponentially relative to salinity. Attached bacteria had highest mean concentrations (3.2–5.5 10⁶ml^?1) at salinities between 0.5 and 5 and were virtually absent at downseam stations (<0.05 10⁶ml^?1). The importance of semidiurnal variability was demonstrated Over the idal cycle, variability of attached bacteria was always greater than that of free bacteria. The analysis of causal models between salinity and free and attached bacteria, showed that the two types of bacteria are uncoupled and that both types have a strong relationship with salimity. Physical processes are thus important controlling factors of the distribution and variability of bacteria. Results suggest that large-scale processes, such as freshwater outflow and residual circulation, largely control free bacteria, whereas short-term and more local processes (e.g., sediment resuspension caused by wind) may also be important in the control of attached bacteria.     

Hydrological and biogeochemical dynamics of the minor and trace elements in the St. Lawrence River

Surface water samples from the St. Lawrence River were collected in order to study the processes controlling minor and trace elements concentrations (Al, Fe, Mn, Cd, Co, Cu, Ni and Zn), and to construct mass balances allowing estimates of the relative importance of their natural and anthropogenic sources. The two major water inputs, the upper St. Lawrence River, which drains waters originating from the Lake Ontario, and the Ottawa River were collected fortnightly over 18 months. In addition, other tributaries were sampled during the spring floods. The output was monitored near Quebec City at the river mouth weekly between 1995 and 1999. Dissolved metal concentrations in the upper St. Lawrence River carbonated waters were lower than in the acidic waters of the tributaries draining the crystalline rocks of the Canadian shield and the forest cover. Biogeochemical and hydrodynamic processes occurring in Lake Ontario drive the seasonal variations observed in the upper St. Lawrence River. Biogeochemical processes relate to biological uptake, regeneration of organic matter (for Cd and Zn) and oxyhydroxide formation (for Mn and Fe), while hydrodynamic processes mainly concern the seasonal change in vertical stratification (for Cd, Mn, and Zn). In the Ottawa River, the main tributary, oxyhydroxide formation in summer governs seasonal patterns of Al, Fe, Mn, Cd, Co and Zn. The downstream section of the St. Lawrence River is a transit zone in which seasonal variations are mainly driven by the mixing of the different water masses and the large input of suspended particulate matter from erosion. The budget of all dissolved elements, except Fe and Zn, was balanced, as the budget of particulate elements (except Cd and Zn). The main sources of metals to the St. Lawrence River are erosion and inputs from tributaries and Lake Ontario. Direct anthropogenic discharges into the river accounted for less than 5% of the load, except for Cd (10%) and Zn (21%). The fluxes in transfer of dissolved Cd, Co, Cu and Zn species from the river to the lower St. Lawrence estuary were equal to corresponding fluxes calculated for Quebec City since the distributions of dissolved concentrations of these metals versus salinity were conservative. For Fe, the curvature of the dilution line obtained suggests that dissolved species were removed during early mixing.     

Influence of an Observed Decadal Decline in Wind Speed on Turbidity in the San Francisco Estuary

Turbidity is an important habitat component in estuaries for many fishes and affects a range of other ecological functions. Decadal timescale declines in turbidity have been observed in the San Francisco Estuary (Estuary), with the declines generally attributed to a reduction in sediment supply to the Estuary and changes to the erodible sediment pool in the Estuary. However, we analyzed hourly wind data from 1995 through 2015 and found statistically significant declines of 13 to 48% in wind speed around the Estuary. This study applied a 3-D hydrodynamic, wave, and sediment transport model to evaluate the effects of the observed decrease in wind speed on turbidity in the Estuary. The reduction in wind speed over the past 20 years was predicted to result in a decrease in turbidity of 14 to 55% in Suisun Bay from October through January. These results highlight that the observed declines in both wind speed and sediment supply over the past 20 years have resulted in reduced turbidity in the San Francisco Estuary from October through January. This decline in turbidity in Suisun Bay potentially has negative effects on habitat for fish like the endangered Delta Smelt which are more commonly caught in relatively turbid water.     

Spatial and vertical trends in sediment-phase contaminants in the upper estuary of the St. Lawrence River

The concentration of selected contaminant trace metals and organic contaminants, namely polycyclic aromatic hydrocarbons (PAHs), normal-alkanes, total polychlorinated biphenyls (PCBs), and other organochlorines, was studied in cores from shallow-water fine-grain sediments from both sides of the maximum turbidity zone (MTZ) in the upper estuary of the St. Lawrence. Average trace metal concentrations in the cores were generally lower in downstream sediments, except for Hg and Pb. Hg levels in the cores were very high, exceeding 0.7 μg g^?1 in core C168 (south shore) and 0.19 μg g^?1 in core LE (north shore). Trace metal concentrations in all the cores were highly variable with depth, but after normalization with reference to iron, the trend was remarkably uniform, thus confirming an important inverse relationship with grain size. A similar lack of a well-defined trend was noted in the profiles of the organic components in the modern sediments. Average PAH values for modern sediments at core sites C168 and LO were 1.05 μg g^?1 and 0.44 μg g^?1, respectively (i.e., less than or equal to those in Lake Ontario and upstream in the river). PCB values far exceeded those in upstream sediments (average: 347 ng g^?1 in core LE and 158 ng g^?1 in C168), but were less than in Lake Ontario. Concentrations of chlordane, heachlorobenzene, and mirex were relatively low and uniform in the modern sections of the cores. The vertical uniformity of both the contaminant profiles and those for Cs-137 (C168) suggests that the sediments are relatively young (i.e., definitely less than 35 yr at C168, and probably even less at LE and LO). Therefore no long-term or historical trend is evident.     

Geological environment of a methane-rich Recent sedimentary basin in the Gulf of St. Lawrence

Two sediment cores collected in Chaleur Trough, Gulf of St. Lawrence are compared in terms of organic geochemistry, sediment texture and foraminifera. One of the cores was collected from a depression and contained methane in the range of 5,970–14,230 ppm, in comparison to 42–106 ppm in the core of open environment. The sediments of the methanerich core are finer, higher in organic carbon, extractable organic matter, plant pigments and contained more diverse foraminiferal assemblages. The results of these geological investigations tend to suggest a relatively fast rate of sedimentation in the depression. This results in the preservation of organic compounds and development of anaerobic subsurface conditions, consequently giving rise to high concentrations of methane through fermentative processes. No other gaseous hydrocarbons were detected hence the possibility of seepage of petroleum gases appears to be remote.     

A review of Middle Ordovician sedimentation in the St. Lawrence Lowland,eastern Canada

Middle Ordovician sediments of the St. Lawrence Lowland, eastern Canada, and its northeastward extension to St-Siméon, are subdivided into the numerous formations of the Chazy, Black River and Trenton Groups. Details of each formation and interpretation of environments of deposition are presented and a coherent model for the development of the upper Middle Ordovician Trenton Group throughout the region is presented. In the southwest, around Montreal, a complete and continuous Middle Ordovician sequence is present and Trenton Group sediments overlie well-developed tidal flat and lagoonal (Black River Group) and mixed shallow subtidal (Chazy Group) sediments. This sequence was deposited on a slowly subsiding, essentially flat, broad shelf environment. Northeastward from Montreal, toward the Montmorency Promontory of the Quebec City area, basal Middle Ordovician sediments become younger and the extent of the shelf area narrowed significantly. The latter resulted in skeletal shoal sediments (lower Trenton Group) developing closer to shore and concomitant less well-developed clastic-rich lagoonal sediments (Black River Group and basal Trenton Group). At Montmorency Promontory the shoal sediments (basal Trenton Group) accumulated along an irregular and rugged coastline. Northeast of the Promontory a steep onshore to offshore profile and rapidly deposited basal inshore clastics (Black River Group) precluded the deposition of skeletal shoals and rapid submergence promoted the early development of deeper shelf (middle and upper Trenton Group) and slope and basin (top Trenton Group, Saint Irénée Formation) sediments. In contrast, corresponding offshore sediments (middle and upper Trenton Group) in the southwest reflect a lower depositional gradient and more gradual subsidence. These patterns of deposition were determined by the interaction of the changing nature of the Ordovician coastline southwest, at, and northeast of the Montmorency Promontory and the variable subsidence rates influenced by the eastward evolving Taconic Orogen.     

Numerical and field study of ship-induced waves along the St. Lawrence Waterway,Canada

Coastal and bank erosion along the St. Lawrence River Waterway in Quebec, Canada, represents a hazard to local communities living along the river banks, as well as to the local fauna habitat. The purpose of this study is to assess the potential impact of the waves generated by long containerships on riverbank erosion and recession at critical sites along the St. Lawrence River Waterway, which have already experienced significant damage. A field study was carried out to investigate the ship-generated hydrodynamics and the various driving mechanisms of the erosion process induced by ship waves. The field measurements provided an assessment of the influence of the length of large vessels by comparing the characteristics of the hydrodynamics fields induced by the passage of two containerships of different lengths. The potential for bank erosion and recession is assessed in terms of the wake erosive energy incident to the shoreline. The field data are compared against analytical results predicted by an empirical model, as well as against a ship-generated hydrodynamics model. Several numerical simulations for quantifying the ship’s drawdown and its effects are also presented.     

Climatic Influences on Autochthonous and Allochthonous Phytoplankton Blooms in a Subtropical Estuary, St. Lucie Estuary, Florida, USA

The St. Lucie Estuary, located on the southeast coast of Florida, provides an example of a subtropical ecosystem where seasonal changes in temperature are modest, but summer storms alter rainfall regimes and external inputs to the estuary from the watershed and Atlantic Ocean. The focus of this study was the response of the phytoplankton community to spatial and temporal shifts in salinity, nutrient concentration, watershed discharges, and water residence times, within the context of temporal patterns in rainfall. From a temporal perspective, both drought and flood conditions negatively impacted phytoplankton biomass potential. Prolonged drought periods were associated with reduced nutrient loads and phytoplankton inputs from the watershed and increased influence of water exchange with the Atlantic Ocean, all of which restrict biomass potential. Conversely, under flood conditions, nutrient loads were elevated, but high freshwater flushing rates in the estuary diminished water residence times and increase salinity variation, thereby restricting the buildup of phytoplankton biomass. An exception to the latter pattern was a large incursion of a cyanobacteria bloom from Lake Okeechobee via the St. Lucie Canal observed in the summer of 2005. From a spatial perspective, regional differences in water residence times, sources of watershed inputs, and the proximity to the Atlantic Ocean influenced the composition and biomass of the phytoplankton community. Long water residence times in the North Fork region of the St. Lucie Estuary provided an environment conducive to the development of blooms of autochthonous origin. Conversely, shorter residence times in the mid-estuary limit autochthonous increases in biomass, but allochthonous sources of biomass can result in bloom concentrations of phytoplankton.     

Oceanic and Hydrologic Influences on Flow and Water Properties in the St. Jones River Estuary,Delaware

Influences of tides, freshwater discharge, and winds on water properties in the St. Jones River estuary (USA), a Delaware National Estuarine Research Reserve, were investigated using multiyear records of sea level, salinity, and turbidity, supplemented by a current profiler time series in 2007. Results demonstrate that instantaneous properties fluctuate with semidiurnal tides and resonant overtides, whereas tidal mean variations are forced by seasonal freshwater inflow and offshore winds. Mean sea level and salinity are highest in summer and vary with seasonal water temperature and rainfall, whereas sea level variability and turbidity are highest in winter on account of storm effects. Salinity and discharge modeling suggest that much (43–65%) of the freshwater resident in the estuary is derived from non-point sources below the head of tide. This diffuse freshwater inflow produces a seaward surface slope and weak mean current, which temporarily reverses under the influence of storm–wind setup within Delaware Bay.     

Holocene development of maritime ombrotrophic peatlands of the St. Lawrence North Shore in eastern Canada

Macrofossil analyses were used to reconstruct long-term vegetation successions within ombrotrophic peatlands (bogs) from the northern shorelines of the St. Lawrence Estuary (Baie-Comeau) and the Gulf of St. Lawrence (Havre-St-Pierre). Over the Holocene, the timing and the ecological context of peatland inception were similar in both regions and were mainly influenced by fluctuations in relative sea level. Peat accumulation started over deltaic sands after the withdrawal of the Goldthwait Sea from 7500 cal yr BP and above silt–clay deposits left by the Laurentian marine transgression after 4200 cal yr BP. In each region, the early vegetation communities were similar within these two edaphic contexts where poor fens with Cyperaceae and eastern larch (Larix laricina) established after land emergence. The rapid transitions to ombrotrophy in the peatlands of Baie-Comeau are associated with particularly high rates of peat accumulation during the early developmental stage. The results suggest that climate was more propitious to Sphagnum growth after land emergence in the Baie-Comeau area. Macrofossil data show that treeless Sphagnum-dominated bogs have persisted over millennia and that fires had few impacts on the vegetation dynamics. This study provides insight into peatland vegetation responses to climate in a poorly documented region of northeastern America.     

Near-Surface Larval and Juvenile Fish in Coastal Habitats: Comparisons Between the Inner Shelf and an Estuary in the New York Bight During Summer and Fall

Exchanges of fish larvae between the inner continental shelf and estuaries can be critical to the functional significance of these habitats as nurseries. We sampled near-surface fishes on the inner continental shelf off New Jersey and in an adjacent estuary during the summer and fall of 2005 and 2006 to evaluate the occurrence and variation in these connections. Very few of the abundant taxa (Anchoa mitchilli, Brevoortia tyrannus, Urophycis regia, Etropus microstomus, Peprilus triacanthus, and Pomatomus saltatrix) were exclusive to either habitat but some did change in relative habitat affinity among seasons. For some species, this was indicative of a departure from the ocean for estuaries (e.g., Micropogonias undulatus) while others used both habitats during the summer and fall (e.g., Syngnathus fuscus, Scophthalmus aquosus, and A. mitchilli). Together, these observations confirm the high degree of connectivity between the near-surface larval fishes from the inner continental shelf and estuaries.