2005 Progress Report: Macrobenthic Process Indicators of Estuarine Condition for the Northern Gulf of Mexico

EPA Grant Number: R829458C008
Subproject: this is subproject number 008 , established and managed by the Center Director under grant R829458
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).

Center: EAGLES - Consortium for Estuarine Ecoindicator Research for the Gulf of Mexico
Center Director: Brouwer, Marius
Title: Macrobenthic Process Indicators of Estuarine Condition for the Northern Gulf of Mexico
Investigators: Rakocinski, Chet
Institution: University of Mississippi Main Campus
EPA Project Officer: Hiscock, Michael
Project Period: December 1, 2001 through November 30, 2005 (Extended to May 20, 2007)
Project Period Covered by this Report: December 1, 2004 through November 30, 2005
RFA: Environmental Indicators in the Estuarine Environment Research Program (2000) RFA Text |  Recipients Lists
Research Category: Water , Ecosystems , Ecological Indicators/Assessment/Restoration

Objective:

Six specific objectives were pursued by the macrobenthic indicator component in the fourth year of the of Consortium for Estuarine Ecoindicator Research for the Gulf of Mexico (CEER- GOM) project: (1) conduct integrated and independent field sampling in 2005; (2) recover from impacts of Hurricane Katrina and personnel loss; (3) continue processing CEER-GOM macrobenthic samples; (4) conduct macrobenthic data reduction through 2004; (5) initiate implementation of a mass balance model of macrobenthic responses to hypoxia; and (6) conduct CEER-GOM related graduate student research. In fulfillment of the first objective, field sampling efforts continued in East Bay and the Weeks Bay/Mobile Bay study areas. During the 2005 study period, benthic sampling was conducted at the six established sites in the Weeks-Mobile Bay system in late July and in late October 2005. In addition, 11 established sites in the East Pensacola Bay system were sampled in late August and in late November 2005. Thus, a total of 39 sites were sampled in 2005, yielding 117 infaunal samples, 39 samples each of pore water nutrients, total organic carbon (TOC), sediment composition, and datasonde profiles. The first 22 pore water nutrient samples were lost due to the ravages of Hurricane Katrina. In fulfillment of the second objective, TOC analysis of 53 TOC samples was outsourced to TDI Brooks International, Inc., of College Station, Texas, a group that also does TOC analyses for the U. S. Environmental Protection Agency (EPA). Also, rather than hire a new taxonomist to replace lost personnel for the remaining duration of the project, a portion of the remaining taxonomic work for the project was outsourced to Dr. Carol Cleveland, who has previously identified benthic samples from the Environmental Monitoring and Assessment Program-Estuaries (EMAP-E) Louisianian Province. In fulfillment of the third objective, raw data were obtained for all mac rofaunal and accompanying samples through 2004. To date sample sorting and size fractionation of extracted macroinverabrates has been completed for all 117 2005 samples. Taxonomic identification is complete for 75 percent of the 2005 samples, and volumetric determinations are 25 percent complete. In fulfillment of the fourth objective, calculation of macrobenthic process indicators and data reduction has been completed for all pooled collections through 2004. In addition, process indicators have been determined for individual grabs for all of the collections through 2004. Existing CEER-GOM macrobenthic datasets through 2004 have been posted to the CEER-GOM ftp site. Daily summaries of continuous dissolved oxygen (DO) data from datasonde site deployment events for use in the integration of 2003 and 2004 CEER-GOM data are well underway. In fulfillment of the fifth objective, the Peters mass balance model has been successfully replicated and examined using the simulation software package, Simile v4.4. In addition, the mass balance model was modified to enable the derivation of unique size-specific mortality coefficients so the model could be tuned to reach a target biomass distribution within some specified time period. Hypothetical effects of DO limitation on ingestion were also introduced within the context of the mass balance model. In fulfillment of the sixth objective, macrofaunal indicators were compared between intertidal Spartina and subtidal habitats and between a set of created marsh islands that had been established for 27 years and a set of nearby natural marsh islands within Davis Bayou, Mississippi. Twenty stations each were located on the created islands and the natural islands; stations were divided equally between intertidal and subtidal habitats. A couple of methodological innovations were implemented for salt marsh habitats, including the use of smaller core samples and standard printed grids for size-sorting infaunal organisms. Total abundance, production potential, and Biomass Size-Spectrum (BSS) residual intercept values differed significantly between created and natural marshes as well as between intertidal and sub tidal habitats. Mean body size differed significantly between habitats but not between created and natural marshes. Turnover time did not differ significantly with respect to either marsh status or habitat. Parallel to differences in total abundance, production potential was higher at the natural marsh and in inter tidal habitat. BSS intercept residuals were generally higher from the natural marsh and from intertidal habitat. The restoration study showed turnover time and production potential values comparable to those from the CEER-GOM salt marsh sites.

Macrobenthic Process-Indicators hypothetically reflect ecosystem function, and thus can be used to assess the effects of eutrophication, hypoxia, and other anthropogenic stressors. The benthic environment plays a pivotal role in the regeneration of nutrients, and macrobenthic communities mediate trophic function by affecting rates, directions, and pathways of exchange and transformation between the water column and sediments. Thus, macrobenthos should provide effective specific indicators of excessive nutrient loading and hypoxia, but macrobenthic functional metrics are seldom used as ecological indicators, and there is a pressing need to develop practical indicators of macrobenthic processes related to ecosystem function. The overall objectives of the Macrobenthic component of CEER-GOM are fourfold:

The main objectives for the Macrobenthic Indicator Component of CEER-GOM are to:

  1. (1) Develop practical methods for quantifying a suite of macrobenthic indicators related to estuarine function that are responsive to eutrophication and hypoxia;
  2. (2) Provide the EPA Benthic Index for the Gulf of Mexico as a benchmark for the validation of novel indicators developed by other CEER-GOM components;
  3. (3) Explore relationships between macrobenthic indicators and functional environmental variables;
  4. (4) Integrate macrobenthic indicators with other novel indicators operating at multiple levels of organization, ranging from genomic to landscape scales.

The specific objectives for Year 4 of the Macrobenthic Indicator Component of CEER-GOM are to:

  1. (1)Conduct Integrated and Independent Field Sampling in 2005;
  2. (2) Recover from Impacts of Hurricane Katrina and Personnel Loss;
  3. (3) Process CEER-GOM Macrobenthic Samples;
  4. (4)Reduce Macrobenthic Data through 2004;
  5. (5) Implement a Mass Balance Model of Macrobenthic Responses to Hypoxia;
  6. (6) Complete CEER-GOM Related Graduate Student Research.

Progress Summary:

Conduct Integrated and Independent Field Sampling in 2005

Macrobenthic sampling efforts in 2005 were maintained as high as in previous years. In addition to typical sampling at the five sites along the 7.5 km transect in East Bay in June 2005, most macrobenthic sampling focused on characterizing East Pensacola Bay and Weeks Bay-Mobile Bay study areas at two times, during the summer index period and in autumn 2005. Benthic sampling was conducted at the six established sites in the Weeks-Mobile Bay system in late July, and again in late October 2005. In addition, 11 established sites in the East Pensacola Bay system were sampled in late August and again in late November 2005. Thus, a total of 39 sites were sampled in 2005, yielding 117 infaunal samples, 39 samples each of pore water nutrients, TOC, sediment composition, and water column profiles. Hurricane Katrina interceded on August 29, 2005, right after an East Bay sampling event. Consequently, the 20 pore water nutrient samples acquired up to that point were lost and many sediment samples were possibly compromised by the lack of refrigeration for 10 days (see Impact of Hurricane Katrina section below). Due to failure of our YSI datasonde during calibration, an alternative YSI sonde without chlorophyll and tur bidity probes was used for getting water column profiles on the last field trip.

Recover from Impacts of Hurricane Katrina and Personnel Loss

Several notable impacts of Hurricane Katrina, which landed on August 29, 2005, impeded the macrobenthic indicator component of the CEER-GOM project. First, sample processing was set back by more than 4 months due to the temporary loss of facilities; the need for project employees to assist with the institutional recovery effort; as well as the loss of an important taxonomist from the project. Although no benthic infaunal samples were lost, the 22 pore water nutrient samples that were taken up to the storm in 2005 were lost, and 22 sediment as well as 37 TOC samples were potentially compromised by 10 days of warm conditions (although these will still be analyzed). The additional loss of TOC analytical capability at the University of Southern Mississippi (USM) Gulf Coast Research Laboratory (GCRL) due to equipment damage and personnel loss required us to seek outside assistance. Consequently, analysis of 53 TOC samples was outsourced to TDI Brooks International, Inc., of College Station, Texas; a group that also does TOC analyses for EPA. Also, rather than hire a new taxonomist for the remaining duration of the project, some of the remaining taxonomic work for the project was out-sourced to Dr. Carol Cleveland, who has previously identified benthic samples from the EMAP-E Louisianian Province. Because of the setbacks incurred from the hurricane and the fact that a full complement of macrobenthic samples was taken in 2005, completion of the project will not be possible within the 1-year extension period as was anticipated (see processing section below), and will require an additional no-cost extension of 6-months in order to recoup.

Process CEER-GOM Macrobenthic Samples

Processing of 2002 Macrobenthic Samples. Sixty macrofaunal samples obtained during the 2002 sampling period included 30 from 10 sites sampled in July 2002 from the Grand Bay National Estuarine Research Reserve (NERR), and two sets of 15 each sampled in August and November 2002 from five sites in East Bay. All of the 2002 samples have been processed, including sorting and quality control for the removal of macrobenthic organisms, size fractionation of macrobenthic invertebrates, identification of size-taxon fractions, and volumetric de terminations. QA/QC procedures have also been completed for these samples.

Processing of 2003 Macrobenthic Samples. One hundred and eight macrofaunal samples from 36 sites were obtained from East Bay between May and November 2003. All of these samples have been processed, including sorting and quality control for the removal of macrobenthic organisms, size fractionation of macrobenthic invertebrates, identification of size-taxon fractions, and volumetric determinations. QA/QC procedures have also been completed for these samples.

Processing of 2004 Macrobenthic Samples. One h undred and fourteen macrofaunal grabs from 38 sites were obtained from East Bay and Weeks Bay-Mobile Bay between May and November 2004. All of these samples have been processed, including sorting and quality control for the removal of macrobenthic organisms, size fractionation of macrobenthic invertebrates, identification of size-taxon fractions, and volumetric determinations. QA/QC procedures have also been completed for these samples.

Processing of 2005 Macrobenthic Samples. One hundred and seventeen macrofaunal grabs from 39 sites were obtained from East Bay and Weeks Bay-Mobile Bay between June and December 2005. Although sample processing was set back considerably by Hurricane Katrina, all samples have been logged in and are currently being processed. To date sample sorting and size fractionation of extracted macroin vert ebrates has been completed for all 117 samples. Taxonomic identification is complete for 75 percent of the samples, and volumetric determinations are 25 percent complete. QA/QC procedures are also underway for these samples.

Sediment Composition Determinations. The processing of sediment samples for sediment composition and grain size parameters has been completed for all 20 sediment samples from 2002, for the 36 sediment samples taken in 2003, and for all 38 2004 sediment samples. Processing of the 39 2005 sediment samples for sediment composition has also been completed (but see caveat re: Hurricane Katrina above).

Sediment TOC Determinations. Sediment TOC determinations have been completed for all of the 2002 and 2003 samples; as well as for 23 of the 38 sediment samples from 2004. TOC analysis capability in the form of personnel and equipment has been recently lost at USM GCRL. Consequently, the remaining 53 TOC samples were outsourced to TDI Brooks International, Inc., of College Station, Texas; who also does TOC analyses for the EPA. These samples have since been completed (but see caveat re: Hurricane Katrina above).

Pore Water Determinations. All 94 pore water samples from 2002, 2003, and 2004 have been analyzed by the University of West Florida (UWF) Center for Environmental Diagnostics and Bioremediation. Extracted pore water samples from the first 22 samples taken in 2005 were lost due to Hurricane Katrina. Fourteen remaining pore water samples taken since the hurricane are extracted and have been transferred to UWF for nutrient analysis.

Missing 2004 Hydrographic Data. To compensate for missing hydrographic data from East Bay in autumn 2004, due to instrument failure in the field, supplementary hydrographic data obtained from East Bay on October 6, and November 5, 2004 were obtained by Mike Murrell of the EPA Gulf Ecology Division in Gulf Breeze, Florida. Surface and bottom measurements of water temperature, salinity, DO, ammonium, nitrite-nitrates, and phosphates were provided from six sites in Blackwater and East Bays, including four CEER-GOM benthic sites.

Reduce Macrobenthic Data Through 2004

Data management activities include continued entry of macrobenthic taxonomic and volumetric data as well as associated collection and environmental data; completion of the trophic classification; and creation of macrobenthic detail and taxonomic database files in MS Access. All collection and sediment data from 2002-2004 have been entered, and entry of 2005 collection and sediment data is in progress. All macrofaunal raw data ha ve been entered through 2004, and entry of data from 2005 macrobenthic samples is underway as they are being obtained.

Data Reduction. CEER-GOM data integration requires that macrobenthic indicators be derived for both pooled and individual grabs. Accordingly, macrobenthic data files from the 10 collections taken in 2002 from the Grand Bay NERR and 10 additional collections from East Bay were post-processed to derive indicator information, including production, community turnover, and BSS parameters. Post-processing of raw macrofaunal data and calculation of benthic process-indicators, including production, community turnover, and BSS parameters, has since been completed for the pooled 2003 and 2004 collections. Further processing of the data was accomplished using three BASIC computer programs that were developed to calculate grab level indicators, the GOM Benthic Index, and trophic structure indicators. Trophic indicators include production-based trophic diversity, as well as mass-based trophic categorical proportions. Subsequent summary data files including macrobenthic process and accompanying environmental point-data for both aggregated and grab levels have been completed for 2003 and 2004 datasets, for use in CEER-GOM data integration efforts. A CEER-GOM workshop for this purpose was held in March 2006, where it was decided to use data through 2004 for integration. Existing CEER-GOM macrobenthic datasets through 2004 have been posted to the CEER-GOM ftp site. Post-processing of the 2005 data has not yet been conducted.

Datasonde DO Data. Daily summaries of continuous DO data from datasonde site deployment events for use in the integration of 2003 and 2004 CEER-GOM data have been undertaken by the macro benthic component. Summary DO metrics calculated for each 24 hour interval include mean, range, minimum, hours < 2 mg/L , and hours < 3 mg/ L. Continuous datasonde periods range between 3 days and approximately 1 month. Although the macrobenthic component was tasked by the Data Core to summarize the open bay sites, we are summarizing all sites to ensure consistency. Summaries for 18 deployment events done in July, August, and October of 2003 in East Bay as well as for 9 events in July and August of 2004 in East Bay have been completed. In addition, daily DO summaries for 10 of 23 deployment events conducted by the crustacean hypoxia component in Weeks Bay and Mobile Bay in 2004 have been completed, and the remaining events are in progress.

Implement a Mass Balance Model of Macrobenthic Responses to Hypoxia

Models should not be made any more complex than they need be in order to make accurate predictions within an acceptable tolerance. Body-size is a fundamental biological attribute because it underlies many autecological rate processes that can be scaled up to the ecosystem level through allometric laws. Thus, a parsimonious approach to modeling ecosystem effects of environmental stress could begin by incorporating body-size dependent processes. The mass balance model published by Peters provides a good starting point for considering effects of hypoxia on the distribution of biomass among different size classes of organisms, a target which is consistent with the macrobenthic process indicators used by the CEER-GOM macrobenthic component. In his original model, Peters simulated the accumulation of biomass as the difference between allometrically scaled gains through ingestion against losses due to egestion, respiration, and mortality (Figure 1). Production (i.e., biomass accumulation) for each size class is obtained from the overall balance of these costs and benefits.

Peters Mass Balance Model

Figure 1. Peters Mass Balance Model. The size of each Wi box represents the biomass of size class i, ac cumulated over time until an equilibrium biomass distribution is reached. A specific and accurate model of hypoxic effects would include specific terms for effects of DO, temperature, food quantity and quality, as well as stochastic mortality. I = ingestion; R = respiration; D = egestion; M = mortality; G = production.

The Peters mass balance model has been successfully replicated and examined using the simulation software package, Simile v4.4. The equilibrium biomass distribution is very sensitive to the mortality function. In Peters’ original formulation, Mortality (Mi) is scaled through the allometric coefficient, F; such that Mi = (BiF/ΣBiF) ΣIi (where ΣIi = food requirements for the animal community). Different equilibrium biomass distributions depend on the value of F; however, the biomasses of small size classes can not be less than those of large size classes when using this mortality function. In contrast, CEER-GOM benthic samples reveal that standing biomasses of large size classes are often greater than those of small size classes in real macrobenthic samples.

Due to the need for plasticity in biomass distributions, another form of the mortality function was required for the mass balance model. Fortuitously, a size-specific mortality function introduced by Peters in a later study enables less constrained biomass distributions. Accordingly, the mass balance model was revised using the size-specific mortality function using the software package, Simile v4.4. This model has different qualitative outcomes, depending on the value of the allometric coefficient, d: (1) the biomass distribution of size classes does not equilibrate until one of the size classes completely dominates after a very long time (≈100 years); and (2) the biomass distribution can be inverted, such that larger size classes contain greater standing biomasses than smaller size classes. This outcome more accurately resembles the outcome of community succession; however, relative biomass distributions that accurately match those observed in nature still cannot be obtained within some specified time frame by using a constant value for d, the allometric mortality coefficient.

Consequently, a mass balance model based on the derivation of unique size-specific mortality coefficients was developed to enable the model to be tuned to reach a target biomass distribution within a specified time period. The existence of unique size-specific mortality coefficients is realistic because different size classes may experience small irregular mortality pressures, which will accrue into large differences in standing biomasses due to high sensitivity of the model to mortality. The required array of unique size-specific mortality coefficients must be found through a simultaneous solution, because any change to a coefficient for a particular size class also affects the biomass trajectories of the other size classes. Thus, the base allometric coefficient corresponding to that used for other processes in the model is adjusted until the output biomass distribution corresponds with the target distribution within the specified model time frame and tolerance (Figure 2). The solution involves minimizing the difference between the model and target biomass distributions. To accomplish this task, the mass balance simulation model was coded into BASIC in a format which incorporates an algorithm that solves for the set of unique size-class specific mortality coefficients. An added advantage of coding is that it facilitates expansion of the model to accommodate other factors, such as hypoxia.

Biomass  Trajectories for Eight Geometric Size Classes Range

Figure 2. Biomass Trajectories for Eight Geometric Size Classes Ranging From 0.46 to 90.0 mg Wet Weight Over an Approximately 2 Year Period, as Projected by the Peters Mass Balance Model Using Unique Size-Specific Mortality Coefficients to Achieve a Realistic Target Biomass Distribution. Dominance shifts from small to large size classes in a nonlinear fashion over the time period. Model output adapted from Simile Version 4.4.

Hypothetical Effects of DO Limitation on Ingestion. Hypothetical effects of DO limitation upon macrobenthic size distributions can be modeled subsequent to some time point when the size distribution in the mass balance model matches that seen in samples from normoxic environments and continues under hypoxic conditions like those actually measured continuously in situ. Previously discussed modifications to the mass balance model will facilitate the conceptual integration of DO stress. Past research shows that oxygen consumption rate (OCR) is hyperbolic with increasing DO and varies interspecifically among bivalves, and that OCR varies with body size in bivalves, errant polychaetes, and amphipods. Since OCR is hyperbolic, oxygen limitation (OL) can be modeled analogously to light limitation in plants. Thus, OL can be modeled through the effects of DO concentration in mg O2 g-1 hour-1 as OCR = (a + b/DO)-1 (Figure 3). The constant, a, physiologically represents several paths of diffusion resistance and biochemical resistance for O2. Previous research with de posit feeding polychaetes found that an autecological effect of low DO is a reduction in ingestion: (1) because the surface area:volume constrains the amount of food that can be metabolically processed (Forbes, 1989); and (2) at least partly owing to the need to decrease time spent on feeding in deference to the need to ventilate (Forbes, et al., 1994). The scaling of this autecological effect is not evenly allometric, at least intraspecifically. Nevertheless, effects of DO limitation on the mass balance dynamics for organisms of a particular size class (i) can be realized through effects of OCR on ingestion (I):

Ii = Gi + Ri + Di; as defined for OCRmax where Ii ≈ OCRmax;
OCRmax = 1/a;
OL = 1 – (OCRDO/OCRmax);

where Gi is growth, Ri is respiration, and Di is egestion for size class i.

If (OLi × (Gi + Ri)) ≤ Gi, then:
Ii,DO = Gi,DO + Ri + Di,DO;
Gi,DO = Gi - [OLi × (Gi + Ri)];
D,DO = Di - (OLi × Di)

If (OLi × (Gi + Ri)) > Gii, then:
Iii,DO = Ri,DO + Di,DO
Ri,DO = Ri – [(OLi × (Gi + Ri)) + Gi]
Di,DO = Di - (OLi × Di)
DGi,DO = degrowth
DGi,DO = Ri – Ri,DO

Hyperbolic Relationship Between  OCR   and Ambient DO

Figure 3. A. Hyperbolic Relationship Between OCR and Ambient DO. Ingestion rate can be modeled through a proportional relationship between OCRDO and OCRmax. B. Time course showing how wide fluctuations in DO could drive the OCR relationship.

Expanding the Hypoxia Mass Balance Model. Before the mass balance model can be used to predict changes in macrobenthic resources and consequent impacts on trophic transfer potential in response to hypoxia, it should be expanded to include more size classes as well as other variables involving DO limitation, water temperature, food quantity and quality, mortality, opportunistic v ersus equilibrium metabolic strategies, respiratory physiology, and possibly trophic structure. A proposal to carry out this work was recently submitted to the National Oceanic and Atmospheric Administration National Centers for Coastal Ocean Science Center for Sponsored Coastal Ocean Research Coastal Hypoxia Research Program.

Complete CEER-GOM Related Graduate Student Research

A CEER-GOM related thesis was recently completed by Ms. Heather Ferguson, entitled “Comparison of Subtidal and Intertidal Macrobenthic Communities between Created and Natural Marsh Islands in the Davis Bayou, Mississippi.” To assess benthic function she used similar methodology to that developed for CEER-GOM but in a different context. A couple of methodological innovations were implemented for applying the methodology in salt marsh habitats, including the use of smaller core samples and standard printed grids for size-sorting infaunal organisms. The following summarizes Heather’s findings:

The general goal of this study was to compare macrofaunal indicators between intertidal Spartina and subtidal habitats and between a set of created marsh islands that have been established for 27 years and a set of nearby natural marsh islands within Davis Bayou, Mississippi. A total of 40 stations were sampled from intertidal and subtidal areas. Twenty stations were located on the created islands and the remaining twenty stations were located on the natural islands. Stations were haphazardly located within target habitats based on where a 1-m2 aluminum box throw-trap landed when thrown from the bow of a 14-foot skiff. Benthic samples were obtained, immediately following the turbidity measurement, from within the 1-m2 throw-trap area using a 5-c m diameter polyvinyl chloride corer with beveled edges that was pushed 5-c m into the sediment. Within 12 to 24 hours of their collection, the 120 benthic cores were sieved and preserved. To separate organisms into established size fractions, they were com pared to standard printed grids (size fractions: 8.0, 6.0, 4.0, 3.0, 2.0, 1.0, 1.5, 0.75, and 0.5 mm) in a Petri dish under a Meiji Techno EMZ-13 dissection microscope. Designated size fraction corresponded to sieve sizes employed in the ongoing CEER-GOM project. Volumes of taxon-size fractions were obtained using a Nikon® image analysis system, following the existing CEER-GOM SOP.

Process indicators examined included macrobenthic abundance, production potential, community turnover-time, mean body-size, and residual intercept from the linearized BSS . Total abundance, production potential, and BSS residual intercept values differed significantly between created and natural marshes as well as between intertidal and subtidal habitats. Mean body size differed significantly between habitats, but not between created and natural marshes. Turnover time did not differ significantly with respect to either marsh status or habitat.

Parallel to differences in total abundance, production potential was higher at the natural marsh and in intertidal habitat. A two-way analysis of variance (ANOVA) of log production potential showed very strong differences in both restoration status (F =14.372; P = 0.001) and habitat (F = 25.423; P < 0.001), with no interaction (Figure 4). At the natural marsh, production potential was markedly higher in both intertidal (mean ± 1 se) (0.1432 ± 0.0140 g m-2 d-1 natural vs. 0.0954 ± 0.0184 g m-2 d-1 created) and subtidal (0.0696 ± 0.0091 g m2 d natural vs. 0.0395 ± 0.0044 g m2 d created) habitats.

Production Potential of Macrobenthic  Organisms (Mean ± 1 se on log scale) for the Four Restoration Status x Habitat  Conditions.

Figure 4. Production Potential of Macrobenthic Organisms (Mean ± 1 se on log scale) for the Four Restoration Status × Habitat Conditions

BSS intercept residuals were generally higher from the natural marsh and from intertidal habitat. The intercepts and slopes of the BSS were strongly correlated among the 40 samples (r2 = 0.948; P < 0.001); and the intercept could be predicted from the slope through the linear relation: Intercept = 0.279 – 0.38 × Slope. Standardized residuals of intercepts from this relationship were examined further within a two-way ANOVA of Status × Habitat. These residuals reflected whether BSS intercepts were high or low relative to the average intercept for a BSS of the same slope. Variances of standardized residuals were homogeneous among treatment groups (Levene’s F = 0.591; P = 0.625). Further, standardized BSS residuals varied strongly and equally between created and natural marshes (F = 15.50; P < 0.001) and between habitats (F = 14.95; P < 0.001), and the interaction effect was non-significant (F = 2.357; P = 0.133) (Figure 5).

BSS Intercept Residual (Mean ± 1 se) for the Four Status × Habitat Conditions.

Figure 5. BSS Intercept Residual (Mean ± 1 se) for the Four Status × Habitat Conditions

Many of the same macrobenthic indicators as those examined in this study have also been measured at other sites representing key habitats in the CEER-GOM study region. Comparisons of these metrics across a wide range of northern G ulf of Mexico habitats provide an opportunity to look for broader landscape-scale patterns. Production values and turnover times vary greatly among the CEER-GOM sites (Table 1). However, values from the restoration study showed similar turnover times and production potentials to those from the CEER-GOM marsh sites in East Bay (Table 1). For example, the turnover time of 30.3 days and production potential of 39,481.43 μg/m2/day at the created subtidal sites were comparable to values from Marsh Creek in East Bay, which is also considered a subtidal site. This site showed a production potential value of 39,575.97 μg/m2/day and a turnover time of 26.0 days in 2002, suggesting near equivalence not only in secondary production, but also in body-size distributions of the infaunal organisms.

Table 1. Comparisons of Production Potential and Turnover Times Between the Marsh Restoration Sites and Selected Representative C EER-GOM Site-Events. Values represent means.

Location
(restoration study)

Prod/m2/Day (micrograms dry weight)

Turnover Time (days)

Location (CEER-GOM)

Prod/m2/Day (micrograms dry weight)

Turnover Time (days)

Created Subtidal

39,481.43

30.3

Grand Bay NERR

13,037.15

51.4

Created Intertidal

95,429.51

28.0

Marsh Pond East Bay

43,499.01

25.8

Natural Subtidal

69,570.16

30.2

Marsh Creek East Bay

39,575.97

26.0

Natural Intertidal

143,162.95

28.1

East Bay (P14)

8,471.11

34.6

Overview of Invited ESA Presentation

All CEER-GOM components were represented relative to macrobenthic indicators at an invited presentation given in August 2005 in Montreal within the session, “Coastal I ndicators of E cological C ondition: I ntegration of S patial S cales” at the 90th Annual Meeting Ecological Society of America – IX International Congress of Ecology (INTECOL). The title of the presentation was: “Comparisons of Macrobenthic Process Indicators of Estuarine Condition in the Gulf of Mexico.” The theme of this presentation maintained that various scaling questions can be addressed using macrobenthic process indicators, including: (1) within-system comparisons across the estuarine gradient-landscape; (2) intra-regional comparisons across estuarine systems; (3) interregional comparisons; (4) bridging indicators across organizational levels; (5) integration with process indicators representing other estuarine subsystems; and (6) allometric scaling from autecological to landscape levels. Examples of how these various scaling issues could be addressed using macrobenthic indicators, often in combination with other CEER-GOM indicators, were presented.

Journal Articles:

No journal articles submitted with this report: View all 13 publications for this subproject

Supplemental Keywords:

RFA, Scientific Discipline, Geographic Area, ECOSYSTEMS, Ecosystem Protection/Environmental Exposure & Risk, Aquatic Ecosystems & Estuarine Research, Ecosystem/Assessment/Indicators, Aquatic Ecosystem, Aquatic Ecosystems, Environmental Monitoring, Ecological Monitoring, Ecological Risk Assessment, Ecology and Ecosystems, Biology, Gulf of Mexico, Ecological Indicators, monitoring, ecoindicator, ecological exposure, estuaries, estuarine integrity, ecosystem monitoring, CEER-GOM, estuarine ecoindicator, benthic indicators, environmental indicators, environmental stress, water quality

Relevant Websites:

http://www.usm.edu/gcrl/ceer_gom/ Exit

Progress and Final Reports:

Original Abstract
  • 2002 Progress Report
  • 2003 Progress Report
  • 2004 Progress Report
  • 2006
  • Final

  • Main Center Abstract and Reports:

    R829458    EAGLES - Consortium for Estuarine Ecoindicator Research for the Gulf of Mexico

    Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
    R829458C001 Remote Sensing of Water Quality
    R829458C002 Microbial Biofilms as Indicators of Estuarine Ecosystem Condition
    R829458C003 Individual Level Indicators: Molecular Indicators of Dissolved Oxygen Stress in Crustaceans
    R829458C004 Data Management and Analysis
    R829458C005 Individual Level Indicators: Reproductive Function in Estuarine Fishes
    R829458C006 Collaborative Efforts Between CEER-GOM and U.S. Environmental Protection Agency (EPA)-Gulf Ecology Division (GED)
    R829458C007 GIS and Terrestrial Remote Sensing
    R829458C008 Macrobenthic Process Indicators of Estuarine Condition for the Northern Gulf of Mexico
    R829458C009 Modeling and Integration