Peddrick Weis

Uptake and distribution of metals in two dominant salt marsh macrophytes, Spartina alterniflora (cordgrass) and Phragmites australis (common reed)

We examined patterns of biomass accumulation and tissue concentrations of five metals—mercury, copper, zinc, chromium, lead—and two elements—carbon and nitrogen—to determine differences in net metal accumulation and distribution between Phragmites australis (common reed) and Spartina alterniflora (cord grass) which were growing intermingled in a contaminated low marsh. Data were collected at 2-month intervals across a growing season (April–October, 1999). Although they comprise only 5–15% of whole plant biomass for both species, roots consistently contained 70–100% of the whole plant metal burdens for both S. alterniflora and P. australis (shoot:root ratio <0.42). Stems and rhizomes had low and similar concentrations between plant species throughout the summer. Leaves of S. alterniflora, however, had consistently greater concentrations of Hg and Cr than those of P. australis. In contrast, the micronutrients Cu and Zn were enriched in P. australis leaf tissue in October, compared to S. alterniflora. Pools of metal in aboveground biomass were similar between plant species, but throughout the season S. alterniflora allocated more of this burden to leaf tissue than P. australis, which allocated more of the aboveground burden to stem tissue, a recalcitrant tissue with lower concentrations but greater biomass. The consistently higher concentrations and total pools of Hg and Cr in S. alterniflora leaf tissue and higher Zn and Cu in P. australis may result from differences in leaf phenology, root-influenced metal availability, or transport of dissolved metals. Because S. alterniflora shifts more of its Hg and Cr load into highly decomposable leaf tissues (as opposed to recalcitrant stems, roots, and rhizomes) this pathway of metal bioavailability would be reduced when S. alterniflora is replaced by P. australis.

Tolerance and Stress in a Polluted EnvironmentThe case of the mummichog

There appear to be costs of embryonic resistance to pollutants opulations of organisms that have been chronically exposed to chemical pollutants may develop increased tolerance, or resistance, to those toxicants. Tolerance may result from genetic adaptation or physiological acclimation to the polluted environment. Although some researchers say that the term resistance should be applied only to genetic adaptation and tolerance to physiological acclimation, other investigators have defined the terms in other ways. Many workers have used the words interchangeably, as we do in this article.

Phosphorus utilization in rainbow trout (Oncorhynchus mykiss) fed practical diets and its consequences on effluent phosphorus levels

Excessive dietary phosphorous (P) concentrations in effluents from aquaculture present a major environmental problem. We therefore studied the effect of dietary P and vitamin D3 on P utilization by rainbow trout-fed practical diets and on P concentrations in the soluble, particulate and settleable components of the effluent from fish tanks. Rainbow trout (average weight: 78 g, initial biomass: 13 kg in 0.7 m3 tanks) were fed for 11 weeks, practical diets that varied in total P, available P, and vitamin D3 concentrations. Soluble, particulate (10–200 μm) and settleable (>200 μm) P in the effluent were sampled every 0.5–6 h for 1–3 days in the third and eleventh weeks of the experiment. Trout in all diets more than doubled their weight after 11 weeks. Increasing the concentrations of available dietary P from 0.24% to 0.88% modestly enhanced growth rate. Feed conversion ratio (FCR) and biomass gain per gram P consumed decreased as dietary P concentrations increased. Carcass P, daily P gain, and plasma P concentrations were lower in fish fed with low P diets. Soluble P concentrations in the effluent peaked immediately after and again 4–6 h after feeding, and is a linear function of available dietary P. No soluble P would be produced during consumption of diets containing less than 0.22±0.02% available P. Above this dietary concentration, soluble P would be excreted at 6.9±0.4 mg/day/kg for each 0.1% increase in available dietary P. Particulate P concentrations in the effluent were independent of dietary P concentrations. Settleable, presumably fecal, P concentrations tended to increase with dietary P concentrations. In trout fed with low P (0.24% available P, 0.6% total P) diets, 60% of total dietary P were retained by the fish and the remaining 40% were excreted in the effluent as settleable P (20–30%) and particulate or soluble P (10–20%). In trout fed with high P (0.59–0.88% available P; 0.9–1.2% total P) diets, 30–55% of total dietary P was retained by fish, and the remaining 15–25% appeared in the effluent as settleable P, 20–55% as soluble P, and 5–10% as particulate P. Vitamin D3 did not affect fish growth nor effluent P levels. Physicochemical management of aquaculture effluents should consider the effect of diets on partitioning of effluent P, the peaks of soluble P concentration following feeding, and the contributions of particulate P to total P in the effluent. Increasing our understanding of how dietary P is utilized and is subsequently partitioned in the effluent can contribute significantly towards alleviating this important environmental and industry problem.

Calcitermin, a novel antimicrobial peptide isolated from human airway secretions

The human airways are protected from pathogenic colonization by a blanket of fluid impregnated with innate antimicrobial effector molecules. Among several previously uncharacterized components, we isolated a peptide that had activity primarily targeting Gram‐negative bacteria. We named the peptide ‘calcitermin’ since its amino acid sequence and mass were equivalent to the 15 C‐terminal residues of the S100 protein, calgranulin C. The antimicrobial activity of calcitermin was enhanced in acidic buffers (pH 5.4) and in the presence of micromolar concentrations of ZnCl2. Analysis revealed a putative zinc‐binding consensus sequence as well as an α‐helical conformation in structure‐promoting solvents.

Tolerance and stress in a polluted environment: The case of the mummichog. [Fundulus heteroclitus]

There appear to be costs of embryonic resistance to pollutants opulations of organisms that have been chronically exposed to chemical pollutants may develop increased tolerance, or resistance, to those toxicants. Tolerance may result from genetic adaptation or physiological acclimation to the polluted environment. Although some researchers say that the term resistance should be applied only to genetic adaptation and tolerance to physiological acclimation, other investigators have defined the terms in other ways. Many workers have used the words interchangeably, as we do in this article.

Lead uptake, distribution, and effects in two dominant salt marsh macrophytes, Spartina alterniflora (Cordgrass) and Phragmites australis (Common reed)

We examined biomass accumulation, tissue concentrations of lead (Pb), and net uptake of Pb in Phragmites australis (common reed) and Spartina alterniflora (salt cord grass) grown under greenhouse conditions in sediment of different Pb concentrations. Sediment and newly emerged ramets of each plant species were collected in April 1999 from Tuckerton, NJ, a relatively clean salt marsh. One-gallon pots were filled with either control sediment (29 microg g(-1) Pb) or Pb-added sediment (68 microg g(-1) Pb), and the sediment moisture was kept saturated along with controlled additions of additional nutrients. At harvest in October, whole plant biomass was 60-85% greater for pots with P. australis than pots with S. alterniflora and a 40-70% reduction in biomass in response to the addition of Pb was observed for both species. In the high Pb treatments, both concentrations and pools of Pb were greater in the leaves of S. alterniflora than in leaves of P. australis at the end of the growing season. In both species, Pb concentrations were higher in lower leaves than upper leaves. The addition of Pb into experimental pots led to over an 800% increase in Pb standing stock for both species. In S. alterniflora, however, significantly more of this pool was allocated to aboveground biomass (leaves and stems) than to belowground biomass (roots and rhizomes). This difference in allocation was more profound at the higher sediment Pb concentration (Pb-added pots). This fundamental difference between the species in response to Pb contamination indicates that metal export into food webs or the water column should be greater in stands of S. alterniflora than in P. australis. These results suggest that in Pb-contaminated, and possibly all metal-contaminated sediments, the replacement of S. alterniflora with P. australis may reduce metal bioavailability by sequestering a greater proportion of its metal burden in belowground tissues which are likely to be permanently buried.

Patterns and processes of mercury release from leaves of two dominant salt marsh macrophytes,Phragmites australis andSpartina alterniflora

The release of mercury (Hg) from leaf tissue was compared between two dominant salt marsh macrophytes,Spartina alterniflora andPhragmites australis. Rates of Hg release were measured for individual leaves from late May to late July, along with concentrations of Hg in leaf tissue, rates of sodium (Na) release, and rates of transpiration. Leaves ofS. alterniflora consistently releasd 2–3 times more Hg than leaves ofP. australis. Leaves ofS. alterniflora also contained greater concentrations of Hg during these months. In contrast toP. australis leaves, rates of Na release were high forS. alterniflora and were correlated with rate of Hg release. Transpiration rates averaged 2.2 times greater forPhragmites as compared toS. alterniflora, and were not correlated with the other variables at the leaf level for either species. Leaf Hg concentration was highly correlated with Hg release for both species, but the slope was significantly greater forS. alterniflora. Monthly differences were profound for all climate and physiological variables measured, with high measurements in May, and lower measurements in June and July. For both species, the highest Hg content was found in lower leaves in May, followed by upper leaves in May. Hg accumulation in leaf tissue and release from both species appear to be greatest in the spring, although differences between the species persist throughout these peak months of the growing season.

Release into the environment of metals by two vascular salt marsh plants

Metals in contaminated salt marshes are mainly locked in the anaerobic layer of sediments, where they are tightly bound as sulfides and organic complexes. Vascular plants survive in saturated soils in part by pumping O2 into their root zones, changing their microenvironment to an oxic one. This, along with chelating exudates, mobilizes metals, allowing uptake by the roots. We compared the common reed Phragmites australis and cordgrass Spartina alterniflora in lab and field studies for ways in which they handle trace metals. Both plants store most of their metal burden in their roots, but some is transported to aboveground tissues. Spartina leaves contain approximately 2-3 x more Cr, Pb, and Hg than Phragmites leaves, but equivalent Cu and Zn. Furthermore, Spartina leaves have salt glands, so leaf excretion of all metals is twice that of Phragmites. In-depth studies with Hg indicate that Hg excretion correlates with Na release but not with transpiration, which is 2.2 x higher in Phragmites; and that more Hg accumulates in early-appearing leaves than in upper (i.e. later) leaves in both species. Spartina thus makes more metals available to salt marsh ecosystems than Phragmites by direct excretion and via dead leaves which will enter the food web as detritus.

Mercury uptake by the estuarine species Palaemonetes pugio and Fundulus heteroclitus compared with their parasites, Probopyrus pandalicola and Eustrongylides sp.

When exposed to methylmercury in the laboratory, grass shrimp, Palaemonetes pugio, parasitized by the isopod Probopyrus pandalicola, accumulated lower concentrations of mercury than their unparasitized counterparts. The parasitic isopod accumulated far less mercury than the grass shrimp. When exposed to mercury in a contaminated field site, mummichogs, Fundulus heteroclitus, parasitized with the nematode Eustrongylides, similarly accumulated lower concentrations of mercury than unparasitized fish, and the parasite similarly accumulated less than the host. The lower uptake by the parasites compared to their hosts is counter to the general view of biomagnification of methylmercury, since parasites are a trophic level above their hosts. The mechanism whereby parasitized animals accumulate less toxicant than unparasitized ones is unknown, but may be partially due to lower metabolic rate.

Endocrine disruption : thyroid dysfunction in mummichogs (Fundulus heteroclitus) from a polluted habitat

Mummichogs (Fundulus heteroclitus) from Piles Creeks (PC), New Jersey (a polluted site), are sluggish and show poorer prey capture and predator avoidance than reference fish from Tuckerton (TK). The behavioral dysfunction of the PC fish may be associated with thyroid impairment due to endocrine disruption. In this study, we compared thyroid histology and thyroid hormones in the two populations and determined experimentally whether the polluted environment could alter thyroid hormone levels. PC fish had larger thyroid follicles, greater follicle cell heights, and contained higher plasma thyroxine (T4) levels than TK fish. However, there were no significant differences in either plasma or tissue triiodothyronine (T3). TK fish held in simulated PC environments had higher plasma T4 and lower plasma T3 than field-sampled fish. PC fish held in clean water had lower plasma T4 and T3 than field-sampled fish. In either case, there was no significant difference in tissue T3 content. The contaminants in PC alter thyroid structure and function, which may relate to the behavioral differences between fish from the polluted and reference sites.