Kreeger ACOE 22 DE Bay Seston Report Final

Analysis of Particulate Nutrients and Seston Weights from 2009 to 2011 at Delaware Bay Oyster Stations Danielle Kreeger, Ph.D Academy of Natural Sciences of Drexel University August 28, 2013 A final report prepared for Rutgers University as part of the U.S Army Corps of Engineers Section 22 Delaware River and Bay Monitoring Study Introduction Population dynamics of oysters, Crassostrea virginica, in the Delaware Estuary are governed by diverse physical and biological factors including salinity, disease prevalence and virulence, predation, recruitment, and food availability and quality Sea level rise associated with climate change has the potential when combined with physical alterations to the ecosystem (e.g., channel deepening), has the potential to affect oysters and other natural resources in various ways These factors, singly or together, could increase the bay’s volume and salinity (which could promote disease) or alter hydrology and associated food regimes (which could affect nutrition and production) As part of a 3-year study to assess oyster and sturgeon conditions in the Delaware River and Bay, the goal of this portion of the study was to characterize seasonal, inter-annual and spatial variability in food conditions for oysters in representative growing areas of Delaware Bay The importance of food supply for larval and adult bivalves is widely recognized; however, little direct evidence exists for food limitation within estuaries, either for adult or larval stages The influence of food quantity and quality on larvae is strongly influenced by the recognized importance of lipids in larval diets to permit successful growth and metamorphosis (e.g., Gallager and Mann, 1986; Pernet et al., 2003; Nevejan et al., 2003; Fern aandez-Reiriz et al., 2006) On the other hand, other studies have pointed to the importance of dietary protein for regulating growth of post-set juveniles (Kreeger and Langdon 1993) or for adults at crucial points in the reproductive cycle, such as during gametogenesis (Kreeger 1993, Kreeger et al 1995) Regardless of which biochemical constituent limits production at different life stages and seasons, modeling work has provided support for the belief that both food quantity and food quality are very important for larval success (e.g., Bochenek et al., 2001; Powell et al., 2002, 2004; Hofmann et al., 2004) and these modeling studies have drawn upon a range of experimental literature (e.g., Thompson and Harrison, 1992; Strathmann et al., 1993; Thompson et al., 1996; Baldwin and Newell, 1995; Hendriks et al., 2003) in aggregate supporting this contention, but direct field evidence is limited (e.g., Bos et al., 2006) Oysters feed on microparticulate material suspended in the water column (seston) Oyster productivity and reproductive condition can be affected by both food quantity and food quality To assess food conditions for oysters, water samples were collected from representative areas containing oyster reefs, filtered, and then the filtered material was analyzed for total suspended Delaware Bay Seston 2009-2011 – Kreeger August 28, 2013 solids (TSS) and particulate organic material (POM, represents food quantity) Additional filtered samples were fractionated for their proximate biochemical composition to determine particulate concentrations of protein, lipid and carbohydrate (represents food quality) Particulate protein, lipid and carbohydrate concentrations were contrasted among each other and as percentages of TSS and POM as further expressions of the bioavailable fractions available to support oyster growth and production Data collected from this study were then used by Rutgers staff to update and refine hydrodynamical models of oyster production that includes food supply along with other factors that drive oyster population productivity (Powell et al 2012) The design of the 2009-2011 sampling program was modeled after a similar earlier assessment that occurred between May 2000 and March 2001, led by Versar In the 2000 Versar study, seston quantity and quality, which were referred to as “nutrients,” were analyzed using methods developed by Dr D Kreeger, Academy of Natural Sciences The 2009-2012 sampling program repeated the earlier assessment using the same seston analysis methods as in 2000, but with more stations (up to 18) and months (up to 9) being sampled to provide better resolution of temporal and spatial variation Methods Field Sampling Program To examine seston quantity and quality, water samples were collected by Rutgers staff at eighteen sites in the Delaware Bay and River once every month in 2009, 2010 and 2011, with the exception of February and December Sites were accessed via the F/V Dredge Monster At each site three replicate 1-gallon jugs of water were retrieved from 30.5 cm below the surface with an Eheim Universal Model 1048 submersible pump and flexible rubber tubing Jugs of water were kept at ambient temperature in coolers while being transported back to the laboratory Detailed station locations and notes on the 2009-2011 field sampling can be obtained from Rutgers Seston Collection Seston is defined as microparticulate material too small to be seen by the human eye These are suspended particles that are large enough to be retained on a glass fiber filter having an approximate retention of 0.7 µm (particle diameter) and small enough to pass through a 100-µm sieve Depending on TSS concentrations, typically between 100 and 1000 ml of water are needed to obtain enough seston per filter for accurate analysis Methods for collecting seston from water samples are described in detail in DK-SOP-23 (Rev 2, 8/06) This is a standard operating procedure prepared by D Kreeger and it is available upon request In summary, seston was collected on prepared glass fiber filters using vacuum filtration of water collected in 4-L jugs from field sampling stations Rutgers staff performed the filtrations within 24 hours of collection, and filters containing seston were added to Petrislides™ for storage in a freezer at -20oC until laboratory analysis at Drexel University For each sample (collection station sampled at a given time,) three replicate jugs were filled and then filtered From each jug, four replicate seston samples were collected on 0.7-µm retention glass fiber filters (47 mm diameter; Whatman type GF/F or equivalent.) The replicate filtration Delaware Bay Seston 2009-2011 – Kreeger August 28, 2013 of each water sample (jug) onto four filters allowed for the separate analysis of seston weight, protein content, carbohydrate content and lipid content (Fig 1) Filters were prepared in advance Filters were pre-combusted at 450oC for at least 24 hr prior to seston filtration A sufficient number of preweighed (to 0.01 mg) filters were also prepared in advance of sampling For each bottle/jug of water, one of the four filter replicates was used for weight-on-ignition and the remaining three filter replicates were used for biochemistry The replicate to be used for weight-on-ignition was preweighed The same balance was used before and after filtering seston Weights were measured only on desiccated samples Seston Analysis One of the four replicate seston-coated filters per Figure Diagram showing how replicate water water jug was used for weight-onsubsamples from a single water sample are ignition analysis, one for protein filtered onto four separate glass fiber filters content, one for lipid content and one for carbohydrate content The weight-on-ignition assay assessed the total seston weight per unit volume (i.e., TSS concentration) and the seston organic content Calculations for seston particulate material (PM, aka TSS), particulate organic matter (POM), and the percentage organic content (%OC) are given below Seston filters for weight analysis were dried at 60 oC for >2 days and weighed (±0.01mg; Sartorius M-9001) Filters were then combusted in a muffle furnace for 48 hr at 450oC and weighed again on the same balance Concentrations of PM (a.k.a total suspended solids, TSS) and POM were calculated with the following formulae: PM (mg/L) = [(dry filter+seston weight) – (dry filter weight)] / (filtered volume) POM = PM – [(ash filter+seston weight) – (dry filter weight)] / (filtered volume) Organic Content = [POM] / [PM] * 100% The concentration of particulate protein, carbohydrate and lipid was measured on separate replicate filters from each water sample This proximate biochemical composition was determined using published methods that have been adapted by Kreeger et al (1997) Protein was measured spectrophotometrically using the bicinchonic acid modification (Pierce test kit, 23225) of the procedure of Lowry et al (1951), standardized with bovine serum albumen Delaware Bay Seston 2009-2011 – Kreeger August 28, 2013 (Pierce 23210) A microplate reader was used for spectrophotometry at a wavelength of 640 nm Carbohydrates were quantified spectrophotometrically (wavelength 480 nm) using the method of Dubois et al (1956), standardized with potato starch (Sigma S 4561) Lipids were measured gravimetrically according to a modification of the technique of Folch et al (1957), whereby dried seston filters were suspended in 10 ml of 2:1 v/v chloroform/methanol, ground for in a Potter Elvehjem tissue grinder tube with PTFE pestle (Wheaton #358039), and then centrifuged at 1000 x g for The supernatant (containing lipid) was collected and received a 20% v/v (final concentration) aliquot of 0.88% KCl to promote phase separation The bottom layer was transferred by pipette to a pre weighed vial, dried at 37oC until constant weight was achieved, and weighed Hexadecanone was used to standardize the lipid procedure The concentration of particulate protein, lipid and carbohydrate in each water sample was expressed relative to the filtered volume to calculate concentrations Each concentration was then divided by the particulate material concentration to calculate the percentage protein, lipid and carbohydrate contents, respectively Statistical analyses were performed with Statgraphics Centurion XVI.I Results from analysis of variance tests are reported as statistical means generated from the pooled variance in each model, and hence these means may differ slightly from arithmetic means Results and Discussion Data collected from a total of 1,465 seston samples are summarized in the Appendix Each row in the Appendix corresponds to one water sample (i.e jug of water) taken from 18 stations (Fig 2) from which were successfully assessed all four main seston attributes (weight, protein, lipid, carbohydrate) As noted above, up to three replicate jugs of water were collected at each station and month, hence, in most cases there are three rows of data per station and month sampling In a few cases, only two jugs of water were collected and filtered successfully, or the full complement of four filters per jug was not obtained (one filter each for weight, protein, lipid, carbohydrate) In a few cases, there was a problem with the laboratory analysis of one of the four metrics Data was only accepted if all four seston metrics were collected successfully per water sample In 2011, some stations were substituted Despite these occasional limitations with collecting, filtering or analyzing samples, >97% of the intended samplings were completed Delaware Bay Seston 2009-2011 – Kreeger August 28, 2013 Figure Fifteen of the 18 sampling stations shown with stars Three additional stations were located further upbay in the tidal Delaware River zone Seston quantity and quality varied widely in space and time across the many stations sampled in this study, seasonally, and to a lesser extent among the three survey years 2009-2011 In several cases, the spatial variation followed the salinity gradient along the axis of the Delaware Estuary, and some differences were apparent between inshore and offshore sampling stations In other cases, specific sites appeared to be consistent outliers, having special characteristics Temporal variation was reasonably consistent, reflecting the expected seasonal variability associated with spring blooms of phystoplankton and fall-winter outwelling of detritus from marshes and rivers These patterns were punctuated by anomalous weather events associated with storms (e.g Hurricane Irene) and record rainfall and runoff during 2011 Seston Quantity - Spatial Variation Averaged among all months and the three years, the concentration of total suspended solids (TSS =particulate matter) varied widely among stations (Fig 3) This spatial variation was examined in several ways First, stations were grouped according to established oyster monitoring zones which tend to span the salinity gradient from lower bay to upper river: 1=lower bay, 2= high mortality beds, 3=medium-high mortality beds, 4= low mortality beds, 5= very low mortality beds, 6=Delaware sites, and 7=upper river sites More seston was present in the upper estuary than in the lower Delaware Bay sites (Fig 4), presumably due to inputs of sediment and particulates from rivers as well as the expected higher concentrations that get trapped in the Estuary Turbidity Maximum zone Delaware Bay Seston 2009-2011 – Kreeger August 28, 2013 Particle Quantity by Station - All Months 2009-2011 Particu late M atter (m g /L ) 50 40 30 20 10 Figure Concentration of particulate matter averaged (± SE) for all years and months at 22 stations in the Delaware Estuary, sampled 2009-2011 Figure Concentration of particulate matter averaged (natural logarithm transformed; ± SE) for all years and months at oyster monitoring zones that extend from the lower bay (1) to upper tidal river (7) in the Delaware Estuary, sampled 2009-2011 Delaware Bay Seston 2009-2011 – Kreeger August 28, 2013 In addition to the inverse relationship between particulate matter concentration and salinity, exemplified along the axis of the estuary (Fig 4), we found significantly greater concentrations of particulates at stations nearer to shorelines than in the middle of the channel or bay (Fig 5), presumably due to landward sources of particulates in river runoff or marshes Of particular interest was the Nantuxent Station, which had the greatest overall concentration of total particulates (mean = 53.6 mg/L, n=86 samples) among all stations (overall mean = 30.0 mg/L, n=1465), averaged among all years and months In general, oyster condition index, which is a measure of meat fatness and energy available for overwintering, was inversely related to the total concentration of particulate matter in the water column, which is a proxy for the abundance of filterable particles for oysters (Fig 5) The Delaware Estuary is a naturally turbid, mud-rich system dominated by coastal marshes and typified by fewer algal blooms than other major American estuaries because of light limitation by turbidity Therefore, much of the particulate material can be in the form of suspended inorganic sediments and the organic fraction can have lower food value Figure Sum of monthly mean concentrations of particulate due to higher amounts matter during the 2009 sampling year at 18 sampling stations For of refractory detritus comparison, average fall oyster condition index is shown at those (see below) These data stations where assessed during 2009 suggest that overall food quantity (PM concentrations) for oysters is inversely related to oyster condition in the Delaware Estuary due to these unusual natural conditions Delaware Bay Seston 2009-2011 – Kreeger August 28, 2013 Seston Quantity - Temporal Variation The concentration of particulate material varied significantly among the three years and also among months (2-way ANOVA, p0.05) with salinity P a rt O rg a n ic M a tte r (m g /L ) Particulate Organic Matter - All Years and Months 14 11 Figure Concentration of particulate organic matter averaged (± SE) for all years and months at 22 stations in the Delaware Estuary, sampled 2009-2011 Seston POM Quality – Temporal Variation Delaware Bay Seston 2009-2011 – Kreeger August 28, 2013 Similar to PM, the concentration of POM showed a repeatable seasonal pattern among the three study years, with greatest concentrations occurring in spring (Fig 8) The concentration of POM was significantly greater (ANOVA, p