Small Lagoon Research Articles

Genetic diversity and historical biogeography of the Maltese wall lizard, Podarcis filfolensis (Squamata: Lacertidae)

Podarcis filfolensis is an endemic lizard from the Maltese archipelago. There is evidence of human-mediated decline and even extirpation of some insular populations of this species. However, information about the intraspecific genetic diversity and phylogeographic patterns of this species is limited. Here we analyze genetic markers from a multi-locus dataset (mtDNA, 2,533 bp; nuclear c-mos gene, 353 bp; 11 microsatellites) for individuals from extant populations of P. filfolensis. Despite generally low genetic variability, two main mitochondrial groupings were clearly identified. In general, individuals from the main island of Malta were genetically distinct from those from Gozo, Comino, Cominotto and Small Blue Lagoon Rock, and also from Linosa and Lampione individuals. Three genetic clusters were detected based on microsatellite data: one was found at higher frequency on Malta, while the other two included samples from the remaining islands, showing some concordance with the mtDNA pattern. A time-calibrated Bayesian tree for the principal mitochondrial lineages indicated strong statistical support for two P. filfolensis lineages that originated in the Pleistocene (105.4–869 Ka). We show that these lineages largely meet the criteria for recognition as evolutionary significant units despite some recent admixture (possibly due to recent translocations between islands). Human disturbance, low genetic variability, evidence of bottlenecks and extirpation on one island indicate that a thorough review of the current conservation status of P. filfolensis would be timely.

Vertical accumulation of potential toxic elements in a semiarid system that is influenced by an abandoned gold mine

The mining zone at El Triunfo, Baja California Sur, Mexico, was exploited for gold extraction for 200 years. This area includes more than 100 abandoned mining sites. These sites contain mine tailings that are highly contaminated with potential toxic elements (PTE), such as As, Cd, Pb, Sb, Zn, and other associated elements. Over time, these wastes have contaminated the sediments in the adjacent fluvial systems. Our aim was to assess the vertical PTE variations in the abandoned mining zone and in the discharge of the main arroyo into a small lagoon at the Pacific Ocean. Sediments were collected from the two following locations in the mining zone near the arroyo basin tailings: 1) an old alluvial terrace (Overbank) and a test pit (TP) and 2) two sediment cores locations at the arroyo discharge into a hypersaline small lagoon. Samples were analyzed by ICP-MS, ICP-OES, and INAA and the methods were validated. The overbank was the most contaminated and had As, Cd, Pb, Sb, and Zn concentrations of 8690, 226, 84,700, 17,400, and 42,600 mg kg−1, respectively, which decreased with depth. In addition, the TP contained elevated As, Cd, Pb, Sb, and Zn concentrations of 694, 18.8, 5001, 39.2, and 4170 mg kg−1, respectively. The sediment cores were less contaminated. However, the As, Cd, Pb, Sb, and Zn concentrations were greater than the concentrations that are generally found in the Earth's crust. The normalized enrichment factors (NEFs), which were calculated from the background concentrations of these elements in the system, showed that extremely severe As, Cd, Pb, Sb, and Zn (NEF > 50) enrichment occurred at the overbank. The TP was severe to very severely enriched with As, Cd, Pb, Sb, and Zn (NEF = 10–50). The sediment cores had a severe enrichment of As, Pb, and Zn (NEF = 10–25). Their vertical profiles showed that anthropogenic influences occurred in the historic sediment deposition at the overbank and TP and in the sediment cores. In addition, the As, Pb, and Zn concentrations in the sediment cores were related to the deposition of fine sediments and organic carbon.

Productivity in natural and artificial habitats in brackish water systems: an example from Aphanius fasciatus populations

1 - Venice Lagoon is characterized by many different shallow-water habitats, where salt marshes represent important habitats for many nektonic species. On the other side, small lagoon islands show a typical landscape dominated by agricultural gardens and orchards, that still host small ditches once used in traditional fishery activities but now abandoned. 2 - Aims of this study is to determine the productivity of these habitats for the nektonic community, referring to the small teleost Aphanius fasciatus (Valenciennes, 1821), listed in Annex II of ‘Habitat’ Directive 92/43/CEE. 3 - One year monthly samplings were performed in four sites: two natural salt marshes and two systems of artificial ditches. All collected fish were photographed and then released. Only a sub-sample was preserved for laboratory analysis. 4 - Data show that artificial habitats host higher biomass of A. fasciatus, yielding higher secondary production respect to natural salt marshes, while P:B ratios vary in accordance to different environmental features and the related life history strategies adopted by the four populations. 5 - Results of this study highlight the relevance of these artificial habitats in the conservation of an important resident fish species.

The diatom flora in Conceição Lagoon, Florianópolis, SC, Brazil DOI:10.5007/2178-4574.2011n40p25

“Lagoa da Conceição” is a small lagoon located at Santa Catarina Island, Santa Catarina State, Brazil (27º 34`S; 48º 27`W). In recent decades, their characteristics have been changed mainly due to the increase in average salinity caused by permanent opening of the canal, in 1982, that connects the lagoon to the sea and the growing urbanization impact of the surrounding areas. The only study on the lagoon phytoplankton was conducted in 1988, showing that diatoms were the most diverse group and were dominant at some periods. This study aimed to make a floristic survey of the Conceição Lagoon diatom community, analyzing its variation over a sampled period. The samples were obtained in 1979, 1980, 1982, and 1994 at six stations and in 2002 at ten stations with a phytoplankton net. One hundred and eight specific and infraspecific taxa were identified belonging to Coscinodiscophyceae, (32), Fragilariophyceae (14) and Bacillariophyceae (62). Six taxa were present in all sampling periods and fifteen at 80% sampled years. The Conceição lagoon diatom flora showed 41% of taxa in common with the Santa Catarina Southern Lagoon Complex. Scanning electron microscopy studies confirmed the presence of the Cyclotella litoralis Lange et Syvertsen and Paralia fenestrata Sawai et Naguno in the lagoon which probably had been misidentified as Cyclotella striata (Kützing) Grunow and Paralia sulcata (Ehrenberg) Cleve respectively in a former survey. Available data are insufficient to explain the distribution of diatom species related to salinity at the Conceição lagoon.

Phosphorus Distribution in the Sediments of Rongcheng Swan Lake, China

Rongcheng Swan Lake is a small lagoon in eastern Shandong Peninsula, China, whose water quality and ecological environment has deteriorated in recent years. The surface and core sediments were collected from Swan Lake to investigate the concentrations and spatial-vertical distribution of total phosphorus (TP) and various P forms. TP concentrations of the surface sediments (0-10 cm) were low, ranging from 79.15 mg kg-1 to 565.12 mg kg-1. TP concentrations in sediments were relatively high in the northwestern and central lake, and low near the sand spit, which was largely influenced by the anthropogenic inputs and sediment grain size. Inorganic P (IP) was the dominant form of TP, and apatite phosphorus (AP) was the major component of IP in surface sediments. At four of the six sediment profiles, the concentrations of TP, organic P (OP) and non-apatite inorganic phosphorus (NAIP) decreased rapidly with depth in the surface 0-10 cm layers, which was related to the increase of anthropogenic inputs in recent 20-30 years. In conclusion, the sediments in northwestern area had great potential for P release in the alkaline water of Swan Lake.

Sedimentology and temporal distribution of microbial mats from Brejo do Espinho, Rio de Janeiro, Brazil

This study covered an annual cycle of the growth of microbial mats in Brejo do Espinho, which is a small lagoon in the State of Rio de Janeiro located near Lagoa Vermelha. Two developmental stages of the microbial mats were observed throughout the study period. These stages presented laminations with colours that varied between yellow, green and reddish brown hues. Their microfabric comprised peloids and micritic lumps, with a predominance of magnesian calcite and evidence of dolomite. The mats also contained other minerals, such as gypsum and halite. Energy dispersive X-ray spectrometer analysis also indicated the presence of a silicate associated with the organic matter and sometimes with carbonates. The first stage was characterised by a gelatinous texture, low mineral content and sparse populations of cyanobacteria that were located only in permanently flooded areas of the Brejo do Espinho. This structure occurred during the drought period and the beginning of the flood period. The second stage exhibited peloids and larger micritic lumps that sometimes formed thin carbonate layers and occurred in the infra- and mesocoastal regions of the lagoon. These structures were observed only during the lagoon drought period. Quantitatively, most represented cyanobacteria were Aphanothece Nägeli 1849 and Chroococccus Nägeli 1849 in both stages. The microbial mats of Brejo do Espinho developed only during the dry season until the start of the lagoon flooding period, which is characterised by shallow water, low turbidity, high salinity, stable substrate and virtually no terrigenous input conditions. In the flooding season, microbial mats were replaced by an intense expansion of Charophyceae algae. Thus, there is a seasonal development of microbial mats linked to extreme hydrologic conditions that limit the growth of other algae during certain periods at Brejo do Espinho.

Watershed Controls on the Geomorphology of Small Coastal Lagoons in an Active Tectonic Environment

This study investigates the relations between watershed precipitation, upstream channel slope, and the geomorphology of 19 small (40 to 18,658 m2), fluvial-incised lagoons in the actively uplifting piedmont near Santa Barbara, CA. Lagoons in the study are funnel-shaped, shallow (<2 m), river-dominated, and enclosed by a sandy to cobble-sized beach barrier for much of the year. Results indicate a strong link between watershed processes and lagoon geomorphology, such that a significant portion of the variability in lagoon area, length, volume, average width, circularity, and lagoon width expansion can be explained by the variability of watershed precipitation and channel slope upstream of the lagoons. Performing multiple regression analysis with watershed precipitation and channel slope as independent variables, coefficients of determination for the power function regressions are 0.88 (lagoon area), 0.88 (lagoon volume), 0.83 (lagoon volume), and 0.74 (average width). Upstream slope is the best single predictor of lagoon geomorphology.

Relative importance of habitat and fishing in influencing reef fish communities across seventeen Pacific Island Countries and Territories

AbstractReef fish assessments were undertaken in 17 Pacific islands to describe the status of finfish resources in 63 villages where fishing is mainly artisanal. Surveys were performed by recording the number and size of edible fish species and benthic composition. Fishing impact was described through six proxies representing level of catch, alternative incomes, degree of commercial catch and country economic development derived from a simultaneous socioeconomic assessment. The relative importance of broadly defined habitat (geographical location, island and reef type, substrate composition) and fishing impact in controlling the distribution of fish trophic groups, families and species was measured through multivariate analysis. The extreme faunistic diversity was shown by the large variation in fish density (difference of up to an order of magnitude) and fish biomass (displaying a 20‐fold difference across the region). Herbivores were dominant in the eastern part of the region, at what we classified as complex islands and at islands with small lagoon and at coastal reefs, while carnivores were dominant at oceanic islands and atolls and at outer reefs. Specific habitat associations were shown for Scaridae, Acanthuridae, Siganidae, Balistidae, Lethrinidae, Lutjanidae and Serranidae. Relative importance and size decrease of several fish families (Mullidae, Scaridae, Lutjanidae and Serranidae) were related to high fishing impact. Acanthuridae and Lethrinidae appeared to have a role as opportunistic groups in impacted sites. The relative impact from fishing and habitat on fishes accounted for, respectively, 20 and 30% of variance, demonstrating the effect of human impacts even at such large scale and taking into account only limited fishing impact variables.

Biochemical and genetic characteristics of suspension-cultured mussels (Mytilus edulis) in relation to byssal thread production and losses by fall-off

Mussel culture relies on the mussel self-attachment capacity through byssus production. By doing so, no cages or containment devices are needed. It has been previously suggested that thread production requires a non- negligible part of the energy expenditure in blue mussels Mytilus edulis. Therefore our work investigates the relation- ships between byssal thread production, mussels energetic reserves and phospholipids profiles in the foot. The relation- ship between thread production and heterozygosity was also examined. The study was realized in a small lagoon of the Iles-de-la-Madeleine, southern Gulf of St. Lawrence, Canada, on four sampling dates between June and September en- compassing the pre- to post-spawning periods. Our results show a significant relationship between the thread numbers and attachment strength. However, no correlations were found between energy reserves, phospholipids composition of the foot or heterozygosity level and byssal production. Our results suggest that mussels in suspension culture in this lagoon were not energy-limited so that the energy reserves did not influence the byssal thread production.

Late Little Ice Age palaeoenvironmental records from the Anzali and Amirkola Lagoons (south Caspian Sea): Vegetation and sea level changes

Two internationally important Ramsar lagoons on the south coast of the Caspian Sea (CS) have been studied by palynology on short sediment cores for palaeoenvironmental and palaeoclimatic investigations. The sites lie within a small area of very high precipitation in a region that is otherwise dry. Vegetation surveys and geomorphological investigations have been used to provide a background to a multidisciplinary interpretation of the two sequences covering the last four centuries. In the small lagoon of Amirkola, the dense alder forested wetland has been briefly disturbed by fire, followed by the expansion of rice paddies from AD1720 to 1800. On the contrary, the terrestrial vegetation reflecting the diversity of the Hyrcanian vegetation around the lagoon of Anzali remained fairly complacent over time. The dinocyst and non-pollen palynomorph assemblages, revealing changes that have occurred in water salinity and water levels, indicate a high stand during the late Little Ice Age (LIA), from AD < 1620 to 1800–1830. In Amirkola, the lagoon spit remained intact over time, whereas in Anzali it broke into barrier islands during the late LIA, which merged into a spit during the subsequent sea level drop. A high population density and infrastructure prevented renewed breaking up of the spit when sea level reached its maximum (AD1995). Similar to other sites in the region around the southern CS, these two lagoonal investigations indicate that the LIA had a higher sea level as a result of more rainfall in the drainage basin of the CS.

Long-term water monitoring in two Mediterranean lagoons as an indicator of land-use changes and intense precipitation events (Adra, Southeastern Spain)

During recent historical times the Adra river delta, a detrital coastal aquifer of nearly 32 km 2 located in a semi-arid, mountainous area of SE Spain, has undergone different changes caused by human activity. Within this context, both the river dynamics in the plain and the geomorphology of the coastline have at various times resulted in the formation of small lagoons. At present only two small (<0.5 km 2) lagoons exist, at the eastern edge of the aquifer, which, although closely surrounded by commercial market-garden greenhouses, are protected under international agreements. During the last 30 years of the twentieth century traditional agricultural irrigation techniques have undergone significant changes to improve their efficiency. Surface-water resources in the Adra river basin are regulated via the Beninar reservoir. In addition, the use of groundwater is increasing progressively. Both these factors affect the recharge of the coastal aquifer. To monitor these changes measurements of electrical conductivity and water level fluctuations have been recorded in these lagoons for the last 35 years (1975–2010). A comparison of the hydrochemical characteristics of the water in the lagoons and of the surrounding groundwater from 2003 to 2010 shows marked differences induced by the different hydrological dynamics in each lagoon, as well as by the hydrogeological impact of changes in land use in the delta. The increase in water demand is a consequence of the extension of irrigated areas from the fluvio-deltaic plain to its slopes, originally occupied by unirrigated crops. A reduction in irrigation return-flow is linked to the use of new irrigation techniques. These modifications affect both the recharge regime of the aquifer and its water quality. Moreover, extreme precipitation events, which are characteristic of Mediterranean semi-arid environments, can affect the lagoons’ hydrological dynamics to a considerable extent. One such example is the unusually rainy period from January to March 2010 (>600 mm). This event, along with other effects, has dramatically lowered the salinity of the water in both lagoons. This case study reveals the extreme vulnerability of deltaic environments and also how lagoons can reflect anthropogenic changes over the whole river basin.

Fishes of Dee Why lagoon: Species composition and factors affecting distribution

Dee Why Lagoon (33o45’S, 151 o19’E) is one of several small coastal lagoons in the Sydney area. It has a maximum surface area of 30 ha and is situated in a heavily urbanised catchment of 500 ha. In 1973 the lagoon and its surroundings were declared a wildlife refuge. The lagoon is closed about 70% of the time by a sand bar across its entrance (NSW Public Works Department, unpublished data). The bar washes away when heavy rain in the catchment raises the water level in the lagoon. On other occasions, the lagoon is deliberately opened to alleviate flooding of property in its catchment (Gordon and Cooke, 1977). Following an ‘opening’, the lagoon’s surface area is reduced to less than 12 ha. The bar is gradually rebuilt by sand transported in the ocean beach ‘swash’ zone. This results in partial flushing of the lagoon by marine waters over extended periods. Opening and flushing subject the lagoon to drastic salinity changes, which together with contaminated storm-water runoff, create an environment characterised by rapid changes in water quality.

CFD Analysis of Mixing in Large Aerated Lagoons

A general CFD model is developed to characterize the flow fields in large aerated lagoons. The power number and flow number of a propeller used in aerated lagoons are validated against lab experiments. Numerical tests in a small lagoon with 8 propellers indicate that the pumping action of propeller can be represented by momentum source effectively. CFD simulations of a large lagoon with the existing 33 propellers and with 16 propellers for a proposed redesign are carried out by substituting one momentum source for each propeller. A local RTD model is developed to predict resident time in both designs based on the converged flow fields. Furthermore, a biological oxygen demand (BOD) model is incorporated to simulate BOD removal in the lagoon. Simulated results show that the proposed design should be more efficient than the existing design in terms of BOD removal per unit power consumption.

Composition, structural characteristics and temporal patterns of fish assemblages in non-tidal Mediterranean lagoons: A case study

The importance of transitional water ecosystems as nursery habitats and feeding grounds for fish species is well-known. Detailed studies of colonization patterns of fish guilds in response to biotic and abiotic drivers are however unevenly distributed among ecosystem types. We address here the temporal variability of fish assemblages in small non-tidal lagoons in the Mediterranean basin. The study was carried out at the Acquatina lagoon (Lecce, Italy) where four stations, situated in two habitat types along a confinement gradient, were sampled twice per month for one year with fyke nets. Forty-five taxa ranging across 20 families were collected, with the most abundant species, Atherina boyeri, accounting for more than 95% of total abundance. Pooling all species together (excluding sand smelt), the structural features of the assemblage, relative abundance of families, and abundance of individual species all showed significant temporal patterns. Mean abundance peaked in Summer and Autumn and fell in Winter, whereas taxonomic richness and diversity were highest in Summer and lowest in Spring. Within the fish assemblage, multivariate ordination showed temporal segregation of species belonging to the same family or genus and expected to be functionally similar, suggesting that they avoid competition for space and resources by timing inward migration and peak occurrence differently. Of the environmental driving forces, which also showed temporal patterns of variation, salinity was the main factor affecting the distribution of individuals and species. The catch of young individuals of several marine species confirmed the role of this small lagoon as a nursery and feeding area, and emphasized the need for further studies.

Management strategies to optimise sustainable clam ( Tapes philippinarum) harvests in Barbamarco Lagoon, Italy

Barbamarco Lagoon is a small lagoon adjoining the Northern Adriatic Sea and is the site of a commercially valuable clam ( Tapes philippinarum) fishery. A three-dimensional (3D) coupled hydrodynamic–ecological model was applied to the lagoon with the objective of assessing impacts on clam food supply, commercial harvests and water quality of different clam rearing strategies, lagoon morphologies and flow regimes. Harvest and net growth to seeding ratios, total harvest value, clearance efficiencies and clam satiety were used to quantify the commercial success of different management strategies, while bottom dissolved oxygen concentrations were used as an indicator of ecosystem health. Increasing exchange with the Northern Adriatic Sea or increasing freshwater inputs into the lagoon improved clam food supply and increased both harvest production and ecosystem health in model simulations of the system. Results indicated that the high spatial and temporal variability of clam production and water quality responses must be considered for a holistic assessment of the outcomes of strategies in the context of ecological and production carrying capacity.

Effects of Salinity on Survival, Growth, Reproductive and Life Span Characteristics of Artemia Populations from Urmia Lake and Neighboring Lagoons

This study deals with effects of different salinities on the survival, growth, reproductive and lifespan characteristics of three Artemia populations from Urmia Lake and small lagoons at the vicinity of the lake under laboratory conditions. Experimental salinities ranged from 75 to 175 g L(-1). Salinity was proved to have significant impact on the majority of the characters studied in this survey. Growth and survival in bisexual A. urmiana and parthenogenetic Artemia from Lake Urmia were significantly higher with respect to the parthenogenetic Artemia from lagoons at most of the salinities tested. Reproductive characteristics such as total number of broods, total offspring number of offspring in each brood and number of offspring at each day of reproductive period reduced with increasing salinity. Moreover higher salinity prolonged the prereproductive period but shortened the total reproductive period. Higher salinities also affected the percentage of encystment and post-reproductive period, showing significantly higher values in parthenogenetic populations in comparison to bisexual A. urmiana.

Tidal, seiche and wind dynamics in a small lagoon in the Mediterranean Sea

Environmental monitoring and hydrodynamic studies were carried out to understand the forcing mechanisms that are responsible for the circulation patterns of the several small coastal lagoons of Sardinia, in the center of the Mediterranean Sea, Italy. The water level observed in the Calich lagoon showed a free-surface oscillation with a semidiurnal period (tide) and a second order oscillation with higher frequency and lower amplitude (seiche). The wind has a local effect on these oscillations and generates a secondary circulation. Numerical analysis confirmed that the dynamics of the lagoon is mainly controlled by a balance between accelerations, barotropic pressure gradients, and bed and wind stresses, and highlighted that the surface seiche is one of the mechanisms responsible for driving residual currents. The employed 2D-horizontal model of lagoon hydrodynamics, forced with tides only at the basin boundary, reproduced the natural mode oscillation period of 0.5 h of the basin. Besides, our study evaluated the accuracy of the simulation of the seiche and wind effects. The plane 2D model, forced with the measured wind stress above the basin surface, simulated stronger seiches by strength and variability in the wind field, in agreement with the measured seiche and wind data. The 5-min time step of our monitoring was, however, too large to quantify accurately the relationship between seiche-induced residual circulation and wind stress. Simulation results indicate that the wind variations at the time scale of minutes could affect the strength of the seiche oscillation. Nevertheless, this variability had insignificant effect on the frequency, suggesting that the oscillatory response is predominantly linear. This analysis showed that tidal, atmospheric and seiche forcing mechanisms are responsible for the circulation patterns of these small Mediterranean wetland areas, generating water level oscillations each one with specific frequency, but with amplitudes of the same order.

Diversity and distribution of bryozoans in the Pelican Cays, Belize, Central America

Thirty-one species of bryozoans were found in mangrove communities in the Pelican Cays. Only in the large lagoon pond at Fisherman’s Cay was the dominant bryozoan a common Caribbean fouling species, Schizoporella pungens. At Northeast Cay, Ridge Cay, Manatee Cay, and Cat Cay, as well as the small lagoon ponds at Fisherman’s Cay, bryozoan species normally associated with shallow reef habitats formed extensive colonies on the submerged hanging roots of red mangroves along banks or undercuts bordering the lagoon ponds. Stylopoma sp., Steginoporella magnilabris, Trematooecia aviculifera, Hippopodina feegeensis, and Rhynchozoon verruculatum were the most abundant species overall. However, presence and relative abundance of these reef species varied from cay-to-cay. The overlapping thalli of Lobophora variegata covered much of the surface on vertical peat banks and on mangrove roots in well-shaded areas. The undersides of the thalli hosted a cryptic bryozoan fauna, consisting of delicate branching and encrusting colonies, which shared some species with both mangrove root and seagrass bryozoan assemblages. Eighteen species, including five undescribed species, were found in the Lobophora habitat.

A case study on trace metals in surface sediments and dissolved inorganic nutrients in surface water of Ölüdeniz Lagoon-Mediterranean, Turkey

Hydro-chemical parameters (salinity, temperature, pH, dissolved oxygen, nitrate, silicate and phosphate) in seawater and major trace metals (Al, Fe, Mn, Cr, V, Zn, Pb, Cu) in sediments were evaluated for the assessment of quality of seawater and sediments in very small lagoon in Mediterranean, Ölüdeniz. Enrichment factors for metals in sediment were in the range of 1.62–8.09, comparable to crustal rock composition. For metals, comparison with literature data revealed relatively low metal concentrations for Ölüdeniz sediments. Correlation analyses on the sediment metal data showed strong correlation in between Cr, Fe and Zn. Surface water salinity slightly decreases within the lagoon, indicating that limited fresh waters inflow to the lagoon. In October, the lagoon waters contained very low phosphate concentrations but measurable values of nitrate and silicate, yielding high NO 3 −/PO 4 3− ratios (90). Very low Chlorophyll- a (biomass indicator) concentrations measured in the lagoon suggest the phosphorus limitation of primary productivity.

Control of scabies, skin sores and haematuria in children in the Solomon Islands: another role for ivermectin.

To assess the effects of a 3-year programme aimed at controlling scabies on five small lagoon islands in the Solomon Islands by monitoring scabies, skin sores, streptococcal skin contamination, serology and haematuria in the island children. Control was achieved by treating almost all residents of each island once or twice within 2 weeks with ivermectin (160-250 microg/kg), except for children who weighed less than 15 kg and pregnant women, for whom 5% permethrin cream was used. Reintroduction of scabies was controlled by treating returning residents and visitors, whether or not they had evident scabies. Prevalence of scabies dropped from 25% to less than 1% (P < 0.001); prevalence of sores from 40% to 21% (P < 0.001); streptococcal contamination of the fingers in those with and without sores decreased significantly (P = 0.02 and 0.047, respectively) and anti-DNase B levels decreased (P = 0.002). Both the proportion of children with haematuria and its mean level fell (P = 0.002 and P < 0.001, respectively). No adverse effects of the treatments were seen. The results show that ivermectin is an effective and practical agent in the control of scabies and that control reduces the occurrence of streptococcal skin disease and possible signs of renal damage in children. Integrating community-based control of scabies and streptococcal skin disease with planned programmes for controlling filariasis and intestinal nematodes could be both practical and produce great health benefits.