Biomass Size Spectra Research Articles

Soil acidity, ecological stoichiometry and allometric scaling in grassland food webs

The factors regulating the structure of food webs are a central focus of community and ecosystem ecology, as trophic interactions among species have important impacts on nutrient storage and cycling in many ecosystems. For soil invertebrates in grassland ecosystems in the Netherlands, the site-specific slopes of the faunal biomass to organism body mass relationships reflected basic biochemical and biogeochemical processes associated with soil acidity and soil C : N : P stoichiometry. That is, the higher the phosphorus availability in the soil, the higher, on average, the slope of the faunal biomass size spectrum (i.e., the higher the biomass of large-bodied invertebrates relative to the biomass of small invertebrates). While other factors may also be involved, these results are consistent with the growth rate hypothesis from biological stoichiometry that relates phosphorus demands to ribosomal RNA and protein production. Thus our data represent the first time that ecosystem phosphorus availability has been associated with allometry in soil food webs (supporting information available online). Our results have broad implications, as soil invertebrates of different size have different effects on soil processes.

Patterns in size and species diversity of benthic macroinvertebrates in Mediterrannean salt marshes

Mediterranean salt marsh macroinvertebrate assemblages are abiotically filtered due to harsh environmental conditions. We hypothesized that in these environmentally fluctuating systems, biotic interactions would have more relevance than abiotic ones and that size-based interactions would dominate. The manuscript focuses on the response to biotic and abiotic factors of 2 diversity metrics: (1) one that relies on species identity (Shannon-Wiener diversity), and (2) another based on the shape of biomass size spectra (size diversity). Benthic macroinvertebrates (organisms >1 mm) were the target group of this study and were sampled monthly in 6 basins during 2 flooding cycles (from October 1997 to July 1999). The high inter-annual variability characteristic of Mediterranean systems revealed the robustness of the observed patterns. Abiotic and biotic interactions appeared to be significant for both diversity metrics, with species diversity more abiotically controlled than size diversity. The relationships between size diversity and environmental variables were more inter- annually stable than those for species diversity. Only water total organic carbon had a robust relation- ship with species diversity, but dissolved inorganic nitrogen and predatory pressure had a robust relationship with size diversity. Additionally, size diversity had a significant succession pattern related to days after flooding (time), whereas species diversity did not. Our results suggest that in abi- otically filtered environments, macroinvertebrate size-based interactions become especially relevant.

Bridging the gap from ocean models to population dynamics of large marine predators: A model of mid-trophic functional groups

The modeling of mid-trophic organisms of the pelagic ecosystem is a critical step in linking the coupled physical–biogeochemical models to population dynamics of large pelagic predators. Here, we provide an example of a modeling approach with definitions of several pelagic mid-trophic functional groups. This application includes six different groups characterized by their vertical behavior, i.e., occurrence of diel migration between epipelagic, mesopelagic and bathypelagic layers. Parameterization of the dynamics of these components is based on a temperature-linked time development relationship. Estimated parameters of this relationship are close to those predicted by a model based on a theoretical description of the allocation of metabolic energy at the cellular level, and that predicts a species metabolic rate in terms of its body mass and temperature. Then, a simple energy transfer from primary production is used, justified by the existence of constant slopes in log–log biomass size spectrum relationships. Recruitment, ageing, mortality and passive transport with horizontal currents, taking into account vertical behavior of organisms, are modeled by a system of advection–diffusion-reaction equations. Temperature and currents averaged in each vertical layer are provided independently by an Ocean General Circulation Model and used to drive the mid-trophic level (MTL) model. Simulation outputs are presented for the tropical Pacific Ocean to illustrate how different temperature and oceanic circulation conditions result in spatial and temporal lags between regions of high primary production and regions of aggregation of mid-trophic biomass. Predicted biomasses are compared against available data. Data requirements to evaluate outputs of these types of models are discussed, as well as the prospects that they offer both for ecosystem models of lower and upper trophic levels.

Linking allometric macrobenthic processes to hypoxia using the Peters mass balance model

Eutrophication alters coastal aquatic food web structure and function through effects of organic enrichment and hypoxia. Macrobenthic communities provide good ecological indicators of impacts on ecosystem function induced by eutrophication. However, effective resource management requires validation of ecological indicators through mechanistic links to specific stressors of concern. Organic enrichment along with subsequent hypoxia typically engenders depauperate macrobenthic communities consisting of small short-lived surface-dwelling organisms. Metabolic ecology theory offers great promise for understanding the role of body size within the context of the trophic dynamics of aquatic ecosystems. Body size is a fundamental ecological trait because it underpins vital rates, which can be scaled up to the ecosystem level through allometric laws. Thus, body size-dependent mechanisms can potentially be used to link macrobenthic indicators to ecosystem consequences of organic enrichment and hypoxia. The Peters mass balance model (PMBM) [Peters, R.H., 1983. The Ecological Implications of Body Size. Cambridge University Press, New York, 329 pp.] provides a platform for projecting stress-induced changes in the distribution of biomass among discrete size classes of organisms. In the PMBM, changes in the distribution of biomass ensue over time from differences between gains due to ingestion and losses due to egestion, respiration, and mortality. Production of biomass results when ingestion exceeds combined losses. In the present study, the PMBM was modified to envisage an inhibitory effect of hypoxia on ingestion by: (1) using unique size-specific mortality coefficients in order to realize target inverted biomass-size distributions during model initialization; (2) linking ingestion rate to the hyperbolic relationship between oxygen consumption rate (OCR) and ambient dissolved oxygen (DO); (3) hypothesizing how oxygen regulation ability follows an allometric scaling rule relative to the supply of DO. If food is unlimited, the most straightforward hypothetical connection between the oxygen consumption rate and ingestion assumes a direct proportional relationship under oxygen limitation. Although small organisms can attain much higher mass-specific rates of oxygen consumption than large ones, previous limited research on oxygen consumption relative to oxygen supply implies that large organisms regulate oxygen intake better than small individuals as ambient DO declines. Counterintuitively, linked ingestion deficits would be accordingly higher for small organisms than large organisms under hypoxia. In pilot simulations incorporating hypothetical ingestion deficits due to oxygen limitation within a modified PMBM, contrasting scenarios emulated continuous DO and water temperature conditions experienced at two shallow subtidal sites for 32 d in summer. Resulting ingestion deficits reduced total biomass and favored large size classes. Effects were stronger under the more hypoxic scenario: total biomass was lower and the biomass-size distribution was more uneven among the size classes. Differences were even more evident in terms of an integrative macrobenthic process indicator, the normalized biomass-size spectrum (NBSS). A realistic hypoxia mass balance model (HMBM) must incorporate various allometric effects that are not necessarily expressed in the same direction relative to body size. A useful resource management tool for anticipating effects of environmental stress on aquatic ecosystem function could be developed from the quantification of trophic transfer potential within a refined PMBM.

A comparison of the mesozooplankton response to hypoxia in Chesapeake Bay and the northern Gulf of Mexico using the biomass size spectrum

Hypoxic (dissolved oxygen concentration < 2 mg L − 1 ) zones are becoming more prevalent in coastal and estuarine systems worldwide. We compared the response of mesozooplankton (> 200 µm) to hypoxia in Chesapeake Bay and the northern Gulf of Mexico using an optical plankton counter (OPC) and pump collections. We predicted that hypoxia would restructure the vertical biomass and biomass size spectrum of mesozooplankton similarly in both ecosystems. Our results showed that the mesozooplankton response to hypoxia may be dependent on the amount of the water column that is hypoxic. In both systems, mesozooplankton appeared to avoid hypoxic water. The Chesapeake Bay biomass size spectrum of mesozooplankton biomass was altered when > 45% of the OPC measurements was made in hypoxic water. Oxic surface water contained smaller-sized mesozooplankton than hypoxic bottom water. There was no consistent shift in size distribution of northern Gulf of Mexico or Chesapeake Bay mesozooplankton biomass in hypoxic water when < 25% of OPC measurements was made in hypoxic water. Pump counts for both systems showed that smaller-sized mesozooplankton were more abundant in surface water. Bottom (hypoxic) pump counts also showed a prevalence of smaller-sized mesozooplankton, but also had a secondary abundance peak at larger sized mesozooplankton. Using a vital staining technique, we found that less than 40% of mesozooplankton collected from hypoxic water in the northern Gulf of Mexico were alive, compared to 70% alive in surface water. This suggests that the OPC may be overestimating mesozooplankton biomass in hypoxic water. It is not possible to estimate from our data whether lower mesozooplankton biomass in hypoxic water is a function of active avoidance or differential predation/mortality. Whatever the case, it is clear that mesozooplankton distribution becomes altered when the majority of the water column becomes hypoxic. The alteration in mesozooplankton distribution has important ramifications for trophic dynamics and the transfer of carbon to higher organisms.

Lago Maggiore oligotrophication as seen from the long-term evolution of its phytoplankton taxonomic size structure

Due to the rapid and common deterioration of aquatic ecosystems, scientists and environmental protection organizations acutely need means capable of producing quantitative estimates for structural deformations of natural communities. Recently, very common biomass size spectra ignore community taxonomic composition, i.e., one of the most important kinds of biological information. Therefore, another very old, but rare in planktonology, method – the traditional taxonomic size spectrum (TTSS) – can be helpful. TTSS, a specific form of size-frequency distribution of taxonomic units, reveals repeating patterns of deep subalpine Lago Maggiore (Italy) phytoplankton taxonomic structure. The general TTSS pattern was safeguarded during 22 annual cycles (1984-2005), when many principal environmental characteristics were changed considerably during the lake oligotrophication. At the same time, the fine structure deformations of this pattern helped us divide the total oligotrophication process into several stages characterized by notable changes of TTSS peaks' proportions. These peak-height alterations were caused by pronounced changes in the species list and overall taxonomic diversity of the lake phytoplankton. The average cell volume decline was found. It was significantly correlated with the total phosphorus descending trend. This cell volume decline was produced by the addition of numerous species into the medium-and-small size fractions. Typical patterns of the stable and transitory stages were differentiated, which could be valuable for environmental protection and diagnostic applications. The central peak height difference between the stable and the transitory periods was statistically significant. Oligotrophication process decomposition into several more homogenous groups of years was supported by quantitative estimators produced by hierarchical cluster analysis. The highest level of the similarity measure (Pearson r) in pairs of annual TTSS was close to the respective estimates found for other lakes. Concomitantly, its minimal level, produced by a specific pair of abnormal years at the beginning and end of the studied process, was found previously only for pairs taken from two different ecosystems (Lakes Kinneret and Tahoe). This way, TTSS can be applied as a quantitative analysis means of the integral natural community structural evolution. Such tools are acutely needed for environmental management, monitoring, and theoretical ecology.

Differences in demersal community structure and biomass size spectra within and outside the Maltese Fishery Management Zone (FMZ)

We examined the protection effect of a long-established fisheries protection zone by studying the demersal communities and the biomass size spectra of specific taxonomic groups. The results and the relevant management implications of the community analysis are discussed within the context of the MEDITS trawl survey program, from which the data was derived. The demersal fishery resources on the muddy bottoms of Maltese trawling grounds were found to be stratified in four main depth ranges: 83 to 166 m (outer continental shelf), 140 to 230 m (shelf break), 270 to 440 m (shallow slope), and 466 to 701 m (deep slope). Significant differences were detected between the inside and outside zones of the outer continental shelf. Stations from this stratum inside the protected zone had twice as much biomass as those outside as well as larger individuals of some species (e.g. elasmobranchs). The depth strata identified do not coincide with those sampled in existing trawl survey programmes in the Sicilian Channel, which were set up without reference to demersal assemblage structure and its relation to depth. It is therefore clear that characterisation of the biotic assemblages is important in order to obtain a better sampling representation of each depth-stratum/assemblage type, and this should be considered in the survey design.

Phytoplankton size structure in transitional water ecosystems: a comparative analysis of descriptive tools

1. Individual size has important implications for the physiology and ecology of phytoplankton. The analysis of size structure is a common approach for studying structure and function of planktonic ecosystems, with applications for the monitoring and conservation of aquatic ecosystem health. Several ways to describe the size structure of phytoplankton communities are used, including size-abundance relationships (SAR), non-normalized and normalized biomass size spectra (BSS), non-normalized and normalized number size spectra (NSS). 2. The main goal of this study was to test the effectiveness of the different tools proposed for describing and monitoring phytoplankton guilds in transitional waters. Comparative analyses were undertaken to evaluate (a) the consistency of each tool in describing the phytoplankton guilds, in terms of statistical significance and agreement with theoretical expectations; and (b) the effectiveness of each tool to discriminate conditions/cases. 3. Eleven transitional water bodies occurring along the eastern and western coasts of the Adriatic Basin were sampled in autumn 2004 and spring 2005. 4. Results obtained highlight that: (1) NSS globally showed higher statistical goodness of fit than BSS; (2) slopes of BSS and NSS, both normalized and non-normalized, were less negative than expected following the linear biomass hypothesis; and (3) the non-normalized NSS shape descriptors were best able to discriminate environmental heterogeneity both between and within transitional water ecosystems. 5. Parameters of NSS are suggested to be consistent descriptors of phytoplankton size structure and potentially important tools for monitoring and conservation of transitional water ecosystems.

Biological properties across the Tasman Front off southeast Australia

Physical, geochemical and biological observations across the Tasman Front off southeast Australia provide the first detailed view of the relationship between physical forcing and biological properties within the frontal system. At the beginning of the austral spring of 2004, high resolution measurements were taken using a CTD and a towed undulating vehicle along transects perpendicular to the Tasman Front at 152 ∘ 00 ′ E , 153 ∘ 00 ′ E and 153 ∘ 30 ′ E . The front was characterised by a sharp surface gradient in physical and biological properties and a sub-surface intrusion of low-salinity water. In general the surface temperature changes across the front from 19 ∘ C in the Coral Sea waters to the north to 17 ∘ C in the Tasman Sea waters over ∼ 10 km . Over the same distance we observed (1) an increase of the mixed layer depth from ∼ 40 to ∼ 100 m ; (2) a 3–8-fold increase in the depth-integrated chlorophyll; (3) an order of magnitude increase in biovolume of particulate matter in the size range of 357– 2223 μ m ; (4) a 2-fold increase in filtered particulate organic matter; (5) a 3 ‰ increase in δ 13 C POM ; and (6) a 4 ‰ increase in δ 15 N POM . The particulate matter in the warmer Coral Sea waters is well approximated by a linear fit of the normalised biomass size spectrum (NBSS) with a slope of between - 0.95 and - 0.99 , while the Tasman Sea waters have a more non-linear and less negative ( - 0.59 to - 0.8 ) spectrum. The low-salinity intrusion that penetrates to within 40 m of the surface between the Coral Sea and Tasman Sea waters is biologically unproductive, with low oxygen, fluorescence and particulate matter counts. The unproductive low salinity intrusion of the Tasman Front contrasts with the highly productive intrusion observed at the Gulf Stream Front off Cape Hatteras, USA. Observations are consistent with Coral Sea and Tasman Sea waters being found in close proximity with steep gradients in biological properties across the front suggesting minimal cross-front mixing. North of the front, the stratified, oligotrophic Coral Sea waters are relatively unproductive, while the vertically well-mixed waters south of the front exhibit strong biological activity.

Structuring pelagic trophic networks from the biomass size spectra

The selection and establishment of the structure (number and compartments, aggregation criteria, and trophic links) of the food webs is a critical task in trophic modelling. The present work proposes a systematic method to structure trophic networks in pelagic food webs. The biomass-size spectrum (BSS) is a well-established approach to analyze the structure of pelagic communities, and the body size is especially related to the ecological role of the organisms in the pelagic environment. To structure food webs, this work uses detailed arrangements of the community in size classes with increasing widths (like Sheldon-type BSS) as first aggregation criteria, and BSS theory as a framework to integrate the available knowledge about feeding selectivity in order to obtain a method to identify the trophic links between compartments. Diet composition matrices were estimated through the combination of a probability of encounter for each food type and a specific probability of ingestion related to the food size selectivity and other food quality characteristics ( e.g., morphology and nutritional quality). The feasibility of this approach has been illustrated through data of size-structured communities extracted from the literature including different planktonic predator guilds (nanoflagellates, cladoceran-dominated zooplankton and copepod-dominated zooplankton) in a high mountain lake (La Caldera, Spain), two subtropical wetland lakes (meso-oligotrophic Laguna Galarza and eutrophic Laguna Iberá, Argentina) and a marine microcosm (Alborán Sea, Mediterranean). The identification of “who eats whom” and “by how much” also allows for more accurate analyses of the trophic control in the BSS. Extensive analyses of the balance between top-down and bottom-up controls were developed for the feeding interactions of the study cases.

Tracking marsh restoration using macrobenthic metrics: implementing a functional approach

Attempts to understand ecological processes within restored saltmarsh ecosystems have increased dramatically in recent years; and it is now generally agreed that marsh restoration success should be gauged relative to the recovery of ecosystem function. Studies of macroinfaunal recovery in created marshes typically employ faunistic metrics to examine colonization and succession. Few studies employ macrobenthic functional metrics. Here, we present an evaluative approach employing macrobenthic functional metrics for use in marsh restoration studies in the context of a comparative study. To illustrate the approach, a four-way comparison of functional and faunistic metrics is made between intertidal Spartina and adjacent 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 Bay, Mississippi. The suite of functional metrics used in this study characterizes the macroinfauna in terms of biological production based and community maturity based attributes. Several production-based attributes (e.g., production potential, normalized biomass size spectrum (NBSS) intercept residuals, total abundance) differed between habitats and between created and natural sites; and community maturity based attributes (e.g., mean size, NBSS slope, faunal turnover rate) differed between habitats. Of the functional metrics, NBSS intercept residuals were most effective for discerning created and natural sites, followed by production potential and total abundance. Of the faunistic metrics, faunal diversity and dominance did not differ between created and natural sites; however evenness was higher at the created site. Diversity and evenness differed significantly between habitats; and dominance almost differed between habitats. Community structure (Bray–Curtis similarity) differed between habitats and between created and natural marshes. This study illustrates how macrobenthic functional metrics can be practical and informative for tracking marsh restoration success. Functional metrics deliver additional insights and appear to be more effective than faunistic metrics. Not only do these functional metrics fulfill the need to understand the role of benthic processes within the context of marsh restoration; they can be related appropriately to other aspects of ecosystem function.

Biomass size spectra of net plankton in the adjacent area near the Yangtze River Estuary in spring

Based on data from survey carried out in spring 2005, the biomass size spectra of net plankton were explored in the adjacent sea of Yangtze River Estuary. Results revealed an approximately continuous size distribution of plankton individuals, from phytoplankton (5–250 μm cell −1 in equivalent sphere diameter (ESD), 15 pg–146 ng C cell −1) to zooplankton (120 μm–2 cm ESD, 115 ng–7.5 mg C ind −1). The normalized spectra (carbon scale) were linear with slope ranged from –0.889 to –0.445, and intercept ranged from 12.866 to 16.863 (all stations together, slope = –0.606, intercept = 19.448), indicating strong deviations from the ideal value (slope = –1.22) of a steady pelagic ecosystem. Correlation analysis presented that intercept and regression coefficient of net plankton size spectra had significant relationship with plankton biomass size diversity.

Ecological change in Great Lakes communities — a matter of perspective

Enormous change in food webs of the Laurentian Great Lakes has been documented from the early 1970s to the 1990s. Variation in abundances of species at all levels in these food webs has been attributed to a variety of causes, including nutrient abatement, invasive species, fishing practices, and climate change. However, this impression of great change is not obvious if food webs are examined from the different perspective of the biomass size spectrum. Despite large shifts in the species structure of zooplankton communities in Lakes Erie and Ontario from 1991 to 1997, zooplankton size spectra have not changed. Furthermore, size spectra for complete food webs of Lake Ontario (Laurentian Great Lake) and Lake Malawi (African Rift Valley Lake) are statistically indistinguishable despite enormous contrast in the geological age and fauna of the two lakes. I conclude that constraints on bioenergetic rate processes and physiological and ecological similarities of like-sized organisms at various hierarchical levels of organization lead to regular and repeatedly observed emergent properties of aquatic ecosystems that are independent of specific species.

Stability of Lake Kinneret phytoplankton structure as evidenced by several types of size spectra

Stability analysis of the aquatic community is among the most important and complicated fields in modern ecology. Application of statistical approaches and modem automated tools has introduced new operational methods for the comparative analyses of aquatic assemblage structure. While much work has been done on two types of biomass size distributions or size spectra (BSS and NBS), the size-frequency distribution of taxonomic units, called here the traditional taxonomic size spectrum (TTSS), has been given much less attention. The composite size spectrum (CSS) described here compares several types of size structures. Two of them (NBS and TTSS) evidenced consistent patterns for Lake Kinneret phytoplankton. The high similarity level of the discussed patterns was estimated quantitatively by cluster analysis. While typical patterns were evident and consistent even during two extremely abnormal years (1997-1998), the fine structure of all size spectra was susceptible to strong environmental impacts. Several types of size spectra used simultaneously provide more comprehensive information describing community structural change.

Regional ecosystem variability drives the relative importance of bottom-up and top-down factors for zooplankton size spectra

The relative effects of top-down and bottom-up drivers of zooplankton size structure were examined in three limnologically diverse regions of Quebec, Canada. Lake productivity drove biomass of small-sized zooplankton (300–1000 µm) in the Eastern Townships and Laurentian regions, which have high total phosphorus gradients, but was not significant in the low-productivity region, Gouin. Fish species composition was found to affect biomass of large-sized (&gt;1000 µm) zooplankton and was the primary factor affecting zooplankton size structure in the low productivity region. When size structure of the zooplankton communities were described as normalized biomass size spectra, only bottom-up factors were significant, as increasing productivity resulted in higher curve peaks and increased parabola curvature. No factors were significantly related to any parameter of the Pareto distribution to describe size spectra. Overall, bottom-up forces were stronger drivers of zooplankton size structure, particularly in regions with wide ranges in lake trophy, while fish predation was more important in regions with low productivity variability.

Assessing the status of shallow lakes using an additive model of biomass size spectra

Abstract Planktonic biomass size spectra were used to summarize the ecological quality of six shallow lakes sampled in spring, early summer and late summer. A simple additive model fitted to the data was used to assess the applicability of the size spectrum theory to shallow lake ecosystems. The additive model replicated the hierarchical pattern of biomass predicted by the predator–prey theory of aquatic production, and was a more appropriate model for predicting biomass size spectra than the frequently used linear regression. Lakes with varying ecological quality were a significant source of variation in the additive model, and further research into using size spectra to monitor ecological quality in shallow lakes is warranted. Specifically, the production of size spectra from a wider range of sites is needed to provide greater statistical validation. The use of size spectra can provide an attractive and cost‐effective way for classifying lake ecosystems because it circumvents the need for difficult taxonomic description. Copyright © 2007 John Wiley &amp; Sons, Ltd.

Changes of macrobenthos composition under different ENSO cycle conditions on the continental shelf off central Chile

The course of environmental conditions and shelf macrobenthic communities off Central Chile (∼36°S) during the strong 1997–98 El Niño (EN) event is compared with a subsequent and basically “normal” period (2002–2003). Changes in macrofaunal community, feeding mode structure, and biomass size spectra are contrasted over time with changes in oceanographic and sediment settings, in order to assess intra- and inter-annual changes in faunal composition during both ENSO periods. During EN, there was a decrease in biomass and abundance of species known to be well adapted to organic-rich, oxygen-deficient environments, such as the interface-feeding polychaete Paraprionospio pinnata. On the other hand the abundance of highly mobile, burrowing polychaetes remained unaffected, or even increased in biomass. The decline of P. pinnata lasted several years after the demise of warm conditions, possibly due to negative interactions with those more mobile burrowing polychaetes. The percent contribution of subsurface-deposit feeders to total biomass increased during EN (49.3±12.4% during summer) and declined only in the summer-fall period of 2002–03 (11.1±4.1%). An opposite trend was observed for interface and surface-deposit feeders. From EN to summer-fall 2002–03 (i.e., normal to low oxygen conditions) the size-structure of the macrobenthos switched from a larger to a smaller-sized assemblage. However, biomass was maintained due to successful recruitment and high abundance of both P. pinnata and the squat lobster, Pleuroncodes monodon. Our results suggest that the shelf macrofaunal community structure exhibit fluctuations at various time scales, and that these changes are more pronounced during and after a strong EN event. In such cases, the effects of such an event may be recorded at latitudes as far south as 36°S, with consequences in the biota lasting for many years after the demise of warm conditions.

Using zooplankton biomass size spectra to assess ecological change in a well-studied freshwater lake ecosystem: Oneida Lake, New York

We explored the sensitivity of three descriptors of zooplankton size spectra (slope, periodic, and Pareto II models) to environmental changes in Oneida Lake, New York, and then used documented environmental changes to model the responses of zooplankton biomass using a general linear model. Using multiple regressions, we identified significant ecological events in Oneida Lake that could affect zooplankton biomass before actual model testing and assessed the three size spectrum models based on their sensitivity to these known variables. The intercept of the slope (linear regression) model was responsive to changes, but the slope was not. The periodic (quadratic) model showed no sensitivity in detecting ecological change. The Pareto II model (probability distribution function) demonstrated the most sensitivity to all ecological variables but was complex to model and there was no direct relationship between its parameters and biological events. The general linear model regression approach proved relatively sensitive to environmental change and had the added benefit of providing a graphical means of biologically assessing differences between years. In general, zooplankton biomass size spectra were responsive to changes in conditions in the Oneida Lake environment, and we believe that size-based approaches have potential as a biotic index in freshwater lake ecosystems.

Day and night ichthyoplankton assemblages and zooplankton biomass size spectrum in a deep ocean island wake

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 322:225-238 (2006) - doi:10.3354/meps322225 Day and night ichthyoplankton assemblages and zooplankton biomass size spectrum in a deep ocean island wake Iain M. Suthers1,*, C. T. Taggart2, D. Rissik1, M. E. Baird3 1School of Biological, Earth & Environmental Science, University of New South Wales, Sydney, New South Wales 2052, Australia 2Department of Oceanography, Dalhousie University, Halifax, Nova Scotia B3H 4J1, Canada 3School of Mathematics, University of New South Wales, Sydney, New South Wales 2052, Australia *Email: i.suthers@unsw.edu.au ABSTRACT: Zooplankton size and larval fish assemblages were compared between locations in the incident free stream and the island wake of Cato Reef, in the south Coral Sea over 6 d in February 1993. Weak incident northward flow of 0.3 m s–1 generated a wake on the lee side of the reef. Total abundance or larval fish diversity did not differ between the lee side and the wake. Myctophids and gonostomatids dominated the catch (85%), while reef-associated taxa represented <2% of the total. There were significantly fewer reef fish larvae in the wake (~25%) than in the free stream, suggesting that reef-related settlement and/or predation may explain the difference. Most of the ichthyoplankton (58 families) were associated with the thermocline (ca. 50 m depth) during day and night. We found significantly steeper slopes of the normalised biomass size spectrum (NBSS, derived from an optical plankton counter) in the wake compared to in the free stream and near the thermocline. The slope was significantly correlated with the shape parameter of the Pareto distribution (r = 0.90), with local light attenuation and with smaller (318 to 883 µm equivalent spherical diameter) zooplankton biomass, consistent with the NBSS slope being a proxy for secondary production. The slope did not vary significantly between day and night despite a 30% daytime reduction in total zooplankton biomass. Steeper slopes were significantly correlated with a greater abundance of larval myctophids and gonostomatids, possibly by fish seeking productive areas and by top-down removal of larger zooplankton. KEY WORDS: Coral Sea · Myctophidae · Optical plankton counter · Diel vertical distribution Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 322. Online publication date: September 20, 2006 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2006 Inter-Research.

Dynamics of macrofaunal body size in a deltaic environment

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 321:55-66 (2006) - doi:10.3354/meps321055 Dynamics of macrofaunal body size in a deltaic environment Ioanna Akoumianaki1,3,*, Sokratis Papaspyrou2, Artemis Nicolaidou2 1Department of Biology, University of Crete, Vassilika Vouton, 71409 Heraklio, Crete, Greece 2Department of Zoology—Marine Biology, University of Athens, Panepistimiopolis 15784, Athens, Greece 3Present address: Institute of Oceanography, Hellenic Centre for Marine Research, Anavissos 19013, Attiki, Greece *Email: akoumio@ath.hcmr.gr ABSTRACT: Macrofaunal density, biomass, and respiration size spectra, as well as density- and respiration-body size allometries, were investigated in a deltaic environment of the eastern Mediterranean (Maliakos Gulf, Greece). Four stations were sampled along a gradient of increasing depth and decreasing water transparency from the river mouth to the plume area in May, August, and November 2000, and February and May 2001. Density and biomass significantly decreased in winter and spring near the river mouth. The shape and peaks of size spectra were temporally variable, indicating that no single factor determines body size at all times. The slopes of the seasonally averaged normalized biomass size spectra gradually decreased from –0.47 at the river mouth to –1.03 in the plume area, clearly indicating a biomass increase with increasing body size towards the river mouth. A flat lower boundary in density/body size relationships at all stations precluded a strong negative regression slope and indicated that the density of small- and intermediate-sized macrofaunal organisms is constrained by perturbations. Regressions of calculated respiration rates against body size were close to 0.75 only at the river mouth during winter, thus indicating that increases in riverine sediment discharges during that period constrain the macrofaunal community. Overall, there was no evidence of energy supply constraints for macrofaunal body size in Maliakos Gulf. Irrespective of whether size spectra and body size allometries conform to global patterns or not, they proved to be sensitive and straightforward descriptors for understanding the macrofauna’s response to the deltaic environment. KEY WORDS: Macrofauna · Size spectra · Biomass · Allometry · Respiration · Coastal zone Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 321. Online publication date: September 08, 2006 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2006 Inter-Research.