Christopher D. Neefus

Integrating seaweeds into marine aquaculture systems: a key toward sustainability

The rapid development of intensive fed aquaculture (e.g. finfish and shrimp) throughout the world is associated with concerns about the environmental impacts of such often monospecific practices, especially where activities are highly geographically concentrated or located in suboptimal sites whose assimilative capacity is poorly understood and, consequently, prone to being exceeded. One of the main environmental issues is the direct discharge of significant nutrient loads into coastal waters from open‐water systems and with the effluents from land‐based systems. In its search for best management practices, the aquaculture industry should develop innovative and responsible practices that optimize its efficiency and create diversification, while ensuring the remediation of the consequences of its activities to maintain the health of coastal waters. To avoid pronounced shifts in coastal processes, conversion, not dilution, is a common‐sense solution, used for centuries in Asian countries. By integrating fed aquaculture (finfish, shrimp) with inorganic and organic extractive aquaculture (seaweed and shellfish), the wastes of one resource user become a resource (fertilizer or food) for the others. Such a balanced ecosystem approach provides nutrient bioremediation capability, mutual benefits to the cocultured organisms, economic diversification by producing other value‐added marine crops, and increased profitability per cultivation unit for the aquaculture industry. Moreover, as guidelines and regulations on aquaculture effluents are forthcoming in several countries, using appropriately selected seaweeds as renewable biological nutrient scrubbers represents a cost‐effective means for reaching compliance by reducing the internalization of the total environmental costs. By adopting integrated polytrophic practices, the aquaculture industry should find increasing environmental, economic, and social acceptability and become a full and sustainable partner within the development of integrated coastal management frameworks.

Songbird response to group selection harvests and clearcuts in a New Hampshire northern hardwood forest

Clearcutting creates habitat for many species of early successional songbirds; however, little information is available on bird use of small forest openings created by group selection harvests. Group selection harvests are increasing on the White Mountain National Forest due to negative public response to clearcutting. The objective of this study was to determine if avian species richness and composition differ between clearcut and group selection openings, and between mature stands and the uncut portions of group selection stands. Point count surveys were conducted during the 1992 and 1993 breeding seasons within six study blocks in the White Mountain National Forest, NH. Each block consisted of a clearcut stand, a group selection stand and a mature stand. Species richness per stand was significantly higher in clearcut openings (p = 0.010) than in group selection openings. Forested areas surrounding group selection openings were similar to mature stands in species richness (p = 0.848) and composition. Our data suggest that, relative to avian use, the group selection system does not provide habitat similar to that created by clearcutting in extensive northern hardwood stands. The group selection system appears to retain much of the mature forest bird community while providing for a limited number of early successional bird species. Gradual replacement of clearcutting with group selection harvests could result in reduced avian diversity across large forested tracts.

Bat habitat use in White Mountain National Forest

In 1992 and 1993, we surveyed the foraging and feeding activity of bat species with broadband bat detectors at 2 foliage heights in 4 age classes of northern hardwood and spruce/fir forest stands in White Mountain National Forest, New Hampshire and Maine. The association of bat activity with trails and water bodies and the effect of elevation were measured. Mist nets, a harp trap, and ultrasonic detectors were used to establish species presence. Bat activity was concentrated at trail and water body edges and was uniform within a forest stand at the same sampling height. Within the forest, bat activity was highest in overmature (>119 yr, 35% of mean bat activity/night) hardwood stands and in regenerating (0-9 yr) stands of both forest types (26% of mean bat activity/night). The majority of bats trapped (56%) were adult male little brown bat (Myotis lucifugus). Our data indicate that a matrix of forest types and age classes including areas of regeneration (clearcuts and group cuts) and overmature hardwood, in combination with trails and water bodies, help fulfill the summer habitat requirements of bats in White Mountain National Forest.

Flowering phenology and compensation for herbivory in Ipomopsis aggregata

The mechanisms and circumstances that affect a plants ability to tolerate herbivory are subjects of ongoing interest and investigation. Phenological differences, and the timing of flowering with respect to pollinators and pre-dispersal seed predators, may provide one mechanism underlying variable responses of plants to herbivore damage. The subalpine wildflower, Ipomopsis aggregata, grows across a wide range of elevations and, because phenology varies with elevation, phenological delays associated with elevation may affect the ability of I. aggregata to compensate for or tolerate browsing. Thus, we examined the response of I. aggregata to herbivory across an elevation gradient and addressed the interactions among phenological delays imposed by damage, elevation, pre-dispersal seed predation and pollination, on I. aggregatas compensatory response. Among high and low elevation populations in areas near the Rocky Mountain Biological Laboratory (RMBL) in Gothic, Colorado, we compared the responses of naturally browsed, artificially browsed (clipped), and unbrowsed (control) plants of I. aggregata. We compared responses in the date of initiation of flowering, timing of peak bloom, floral display, nectar production and sugar concentration, oviposition and fruit destruction by the pre-dispersal seed predator Hylemya sp. (Anthomyiidae), fruit production, and aboveground biomass production. Clipping had the greatest effect on reproductive success and clipped plants at high elevation exhibited the lowest tolerance for herbivory. The effects of browsing appear to be mediated by flowering phenology, and both browsing and elevation delayed flowering phenology. Time needed for regrowth delays flowering, and thus affects the overlap with seed predators and pollinators. As a result of delayed flowering, naturally browsed and clipped plants incurred lower rates of seed predation. In the absence of seed predation, plants would exhibit a lower tolerance to herbivory since naturally and artificially browsed plants had fewer fruits destroyed by Hylemya larvae. We provide additional evidence that, for populations near the RMBL, clipping and natural browsing do not have the same effect on I. aggregata plants. This may be due to the selection of larger plants by herbivores. Although under some conditions plants may tolerate browsing, in areas where the growing season is short a phenological delay imposed by damage is likely to significantly reduce plant fitness. Identifying the mechanisms that allow plants to tolerate herbivore damage will help to develop a general framework for understanding the role of tolerance in plant population and community dynamics, as well as plant-herbivore interactions.

Dietary Variation in the Mexican Free-Tailed Bat (Tadarida brasiliensis mexicana)

In a field experiment designed to evaluate dietary variation in Mexican free-tailed bats ( Tadarida brasiliensis mexicand ) we found that lactating females fed largely on coleopter-ans and lygaeid bugs during evening feeding bouts and mostly on moths during morning feeding bouts. These results suggest that interpretations of food habits in this and other species may be biased unless samples from both nightly feeding bouts are included in the analyses. Diets of different individuals during the same feeding bout were strikingly similar, suggesting that lactating females either fed in the same general habitats or that they encountered and preferentially fed on similar prey items among those available. Bats captured upon return from evening feeding bouts produced significantly more fecal pellets than those captured following second feeding bouts. This difference suggests that either more food is eaten in the first feeding bout or, alternatively, highly chitinous insects such as coleopterans and lygaeids contribute more to fecal matter than relatively soft-bodied moths. We found no significant relationship between hardness of prey and number of pellets produced. Individual bats produced an average of 2–3.6 insects/pellet, but no consistent relationship was found between the number of insects eaten and the number of fecal pellets produced. Our analysis indicates that at least five pellets are needed to establish the number of insect taxa (families) consumed by a bat. Results from this study suggests that future research on food habits of insectivorous bats should examine fecal pellets or stomach contents from evening and morning feeding bouts to fully characterize the diet of a given species.

An improved method for estimating R-phycoerythrin and R-phycocyanin contents from crude aqueous extracts of Porphyra (Bangiales, Rhodophyta)

One frequently-cited method for determining phycoerythrin (PE) and phycocyanin (PC) contents from crude aqueous extracts of red seaweeds utilizes peaks and troughs of absorbance spectra. The trough absorbance values are used to establish a linear or logarithmic baseline attributable to background scatter of particulate cellular debris not removed by centrifugation. Pigment contents are calculated by subtracting baseline values from PE and PC absorbance peaks. The baseline correction is intended to make the method independent of centrifugation time and/or speed. However, when crude extracts of Porphyra were analyzed using this protocol, R-PE and R-PC estimates were significantly affected by centrifugation time, suggesting that the method was not reliable for the genus. The present study has shown that with sufficient centrifugation, background scatter in Porphyra extracts can be removed, the remaining spectrum representing the overlapping absorbance peaks of water-soluble pigments in the extract. Using fourth derivative analysis of Porphyra extract absorbance spectra, peaks corresponding to chlorophyll, R-PE, R-PC, and allophycocyanin (APC) were identified. Dilute solutions of purified R-PE, R-PC and chlorophyll were scanned separately to identify spectral overlaps and develop new equations for phycobilin quantification. The new equations were used to estimate R-PE and R-PC contents of Porphyra extracts and purified R-PE, R-PC and chlorophyll solutions were mixed according to concentrations corresponding to the sample estimates. Absorbances and fourth derivative spectra of the sample extract and purified pigment mixtures were compared and found to coincide. The newly derived equations are more accurate for determining R-PE and R-PC of Porphyra than previously published methods.

Changes in composition of spider orb web sticky droplets with starvation and web removal, and synthesis of sticky droplet compounds

SUMMARY The sticky spiral of araneoid spider orb webs consists of silk fibers coated with adhesive droplets. The droplets contain a variety of low-molecular-mass compounds (LMM). Within a species, a fairly consistent ratio of LMM is often observed, but substantial variability can exist. To gain insight into factors influencing LMM composition, spiders of three araneid species were starved and LMM from their webs were analyzed for changes in composition. To determine if these changes were consistent with the spiders ability to synthesize the different organic LMM, synthetic capacities were estimated following the feeding of radiolabeled metabolites. Some changes in droplet composition were broadly consistent with differing synthetic capacities: molar percentages of less readily synthesized compounds (e.g. choline, isethionate, N-acetyltaurine) typically declined with starvation, at least during a portion of the imposed fast, while more readily synthesized compounds (e.g. GABamide, glycine) tended to increase. Most striking was the apparent partial substitution of N-acetylputrescine by the more readily synthesized GABamide in fasting Argiope trifasciata. However, departures from expected compositional shifts demonstrated that synthetic capacity alone does not adequately predict sticky droplet compositional shifts with starvation. Moreover, feeding controls exhibited some changes in composition similar to starving spiders. As the webs of both feeding and starving spiders were removed for chemical analysis and could not be recycled, the loss of LMM contained in these webs likely contributed to similarities between treatments. In addition, feeding spiders molted, oviposited and/or built heavier webs. The added metabolic demands of these activities may have contributed to changes in composition similar to those resulting from starvation.

Identification of north-western Atlantic Porphyra (Bangiaceae, Bangiales) based on sequence variation in nuclear SSU and plastid rbcL genes

Abstract Six species of Porphyra have commonly been recognized in the north-western Atlantic from Long Island Sound to the Canadian Maritimes: P. amplissima, P. leucosticra, P. linearis, P. miniata, P. purpurea, and P. umbilicalis. Distinguishing them with certainty has been problematic. A DNA-based system of molecular identification was developed using partial sequences of the nuclear small subunit ribosomal RNA gene (SSU) or the plastid ribulose-1,5-bisphosphate carboxylase–oxygenase large subunit gene (rbcL). Multiple samples of each taxon were surveyed for intraspecific variation. Intraspecific SSU divergences for Porphyra ‘leucosticta’, P. ‘miniata’, P. ‘umbilicalis’, and P. ‘purpurea’ ranged from 0% to 1%. There was more variation for P. ‘amplissima’ (0–2.1%) and P. ‘linearis’ (0–3.5%); however, each taxon was monophyletic. No intraspecific differences were observed for these taxa in rbcL (one to eight samples per taxon). These sequences were compared with P. yezoensis U51, introduced to Maine, and with P. ‘dioica’, a north-east Atlantic Porphyra easily confused with P. ‘purpurea’. To discriminate between P. ‘purpurea’, P. ‘umbilicalis’, and P. ‘leucosticta’, SSU variation was used to design primers for the Allele-Specific Polymerase Chain Reaction™. With molecular tools, we could classify over 80% of the monostromatic specimens surveyed, but the residue of unidentifiable specimens may indicate the existence of further monostromatic species in the north-west Atlantic. Porphyra ‘purpurea’ was found to occur further south than previously recorded. A morphologically cryptic Porphyra was discovered at Herring Cove, Nova Scotia, Canada.† Phylogenetic analyses using SSU or rbcL sequences showed ‘soft incongruence’ between gene trees, i.e. the topologies of the phylograms were similar but not identical, with only weak to moderate bootstrap support for the nodes that differed. Both trees strongly supported a clade including P. ‘purpurea’, P. ‘umbilicalis’, P. ‘linearis’, and P. ‘dioica’. Porphyra sp. Herring Cove was allied with the remaining Porphyra taxa in the SSU tree. The rbcL phylogeny was less well resolved, consisting of a polytomy of a P. ‘purpurea’–P. ‘umbilicalis’–P. ‘linearis’–P. ‘dioica’ clade, Porphyra sp. Herring Cove, a clade comprising P. ‘amplissima’ and P. ‘miniata’, and a P. ‘suborbiculata’–P. ‘leucosticta’–P. yezoensis clade.

Evaluation of the bioremediatory potential of several species of the red alga Porphyra using short-term measurements of nitrogen uptake as a rapid bioassay

Rates of inorganic nitrogen uptake by three Northeast US and three Asian species of Porphyra were compared in short-term incubations to evaluate potential for longer term and larger scale examination of bioremediation of nutrient-loaded effluents from finfish aquaculture facilities. The effects of nitrogen (N) species and concentration, temperature, acclimation history, and irradiance were investigated. Uptake rates increased ca. nine-fold from 20 to 150 μM N. Nitrate and ammonium uptake occurred at similar rates. Irradiance had a strong effect, with uptake at 40 μmol photons m−2 s−1only 55% of uptake at 150 μmol photons m−2 s−1. N-replete tissue took up inorganic nitrogen at rates that averaged only 60% of nutrient-deprived tissue. Although there were species (P. amplissima > (P. purpurea = P. umbilicalis)) and temperature effects (10 °C>5 °C>15 °C), interactions among factors indicated that individual species be considered separately. Overall, P. amplissima was the best Northeast US candidate. It took up ammonium at faster rates than other local species at 10 and 15 °C, two temperatures that fall within the expected range of industrial conditions for finfish operations.

Cryptic diversity of Ulva (Ulvales, Chlorophyta) in the Great Bay Estuarine System (Atlantic USA): introduced and indigenous distromatic species

Distromatic foliose blades of the algal genus Ulva are notoriously difficult to identify due to their simple morphologies and few diagnostic characteristics that often exhibit intraspecific variation and interspecific overlap. Hence, species differentiation is difficult and diversity estimates are often inaccurate. Two major goals of this study were to assess the diversity of distromatic Ulva spp. in the Great Bay Estuarine System (GBES) of New Hampshire and Maine, USA, and to compare historical and present day records of these species. Molecular analysis (using ITS sequences) of field-collected specimens revealed four distinct taxa: Ulva lactuca, U. rigida, U. compressa, and U. pertusa. Prior to molecular screening, Ulva lactuca was the only distromatic Ulva species reported for the GBES. Ulva pertusa and the foliose form of U. compressa are newly recorded for the Northwest Atlantic, and the range of U. rigida has been extended. Molecular analysis of historical herbarium voucher specimens indicates that U. rigida, U. pertusa, and the foliose form of U. compressa have been present in the GBES since at least 1966, 1967, and 1972, respectively. The distromatic morphotype of U. compressa is found only in low salinity areas, which suggests that salinity may influence its morphological development. Molecular and morphological evaluations are critical if we are to distinguish between cryptic taxa, accurately assess biodiversity, and effectively monitor the spread of non-indigenous macroalgae.