Coastline ecosystems on Oahu,Hawaii

Summary Coatline ecosystems on Oahu, Hawaii were described in terms of vegetation composition and structure, and environmental components such as climate, physiography, exposure, substratum, and ground water. Vegetation patterns were related to these environmental components. Relevés were established in 22 study areas around Oahu to study the broader patterns of vegetation and environment, and 2 m wide belt-transects were laid out in 16 areas to study structural and floristic zonation from the ocean edge to the limit of the strand flora inland. Physiographic position, substrate type, wind exposure and climate (through climate-diagrams) were determined for each site. Soil parameters determined along the transects were salt concentration, pH, organic carbon, moisture equivalent, soil moisture at 15 atmospheres pressure, and available moisture.Three levels of pattern in vegetation distribution were inferred. First, there were similarities and differences between study areas in terms of vegetation composition and structure, and environmental components. Thirteen ecosystem-classes were recognized on the bases of dominant species and landform: Hibiscus ecosystem on beach flat, Scaevola on dunes, Scaevola on talus and alluvium, Scaevola on raised coral rock, Scaevola on rocky basalt coast, Chloris-Sida on talus, Prosopis on dunes, Prosopis on talus and alluvium, Prosopis on tuffaceous headland, Chloris-Prosopis on dune and clay flat complex, Batis on mud flats, Rhizophora on tidal flats, and Scirpus-Eichornia in fresh-water pond.A second level of pattern was that of zonation into physiognomic zones, and a third that of floristic zonation or change in species composition with distance from sea. Only seven ecosystems, representing five ecosystem-classes (Scaevola on dunes, Scaevola on coral rock, Prosopis on dunes, Prosopis on talus and alluvium, and Prosopis on tuffaccous headland), showed distinct physiognomic zones. But all emerged ecosystems showed floristic zonation.The distribution of the ecosystems coastwise is most broadly related to rainfall and drought patterns, to exposure to wind and surf, and to salinity of soil and water. Hibiscus ecosystems occur in wet, protected beach flats of terrigenous sand, found in windward coasts; Scaevola ecosystems in areas exposed to intense wind and salt spray; Prosopis ecosystems and their variant, Chloris-Prosopis ecosystem, in droughtly areas of the leeward coast; Chloris-Sida ecosystem on rocky soils in the same droughty climate; Batis ecosystems on mud flats of high soil- and ground-water salinity; Rhizophora ecosystems in protected shorelines subject to tides; and Scirpus-Eichornia ecosystem in still fresh water.Salt concentration decreased markedly with distance inland in fine-textured soils, but showed only slight increases or decreases in coarse-textured dune soils. Organic matter showed increases, with three transects registering increases of 15% organic C at peak portions. pH was very variable; alkaline values arising largely from a high proportion of calcium carbonate parent material or high salt content and more acid values arising from greater organic matter incorporation. The range of many of the strand species has been increasingly limited by direct disturbance and indirectly by the seaward encroachment of introduced Prosopis. But they are still persisting (in larger or smaller numbers) in Scaevola ecosystems.     

Community structure and habitat associations of parrotfishes on Oahu,Hawaii

Despite their ecological importance as bioeroders and their economic importance in commercial, artisanal, and recreational fisheries, there have been relatively few studies on parrotfish (Scaridae) ecology in Hawaii. Belt transects were conducted around the island of Oahu to survey current parrotfish distributions, size structure, species composition and associated habitats. Scarid communities in this heavily fished region are dominated by smaller species and smaller individuals within all species. Specific habitat characteristics such as rugosity, substrate diversity, and percent live coral cover were positively correlated with scarid numerical abundance. Scarids, however, were patchily distributed and were often absent from preferable habitats, suggesting that intense fishing pressure may be an important factor preventing these fish from fully exploiting available habitats. This study is the first thorough, broad-scale investigation of scarid community structure in Hawaii, and provides important information that has management and conservation implications for parrotfish in Hawaii and throughout tropical coral reef ecosystems.     

Coliphage and indigenous phage in Mamala Bay, Oahu, Hawaii.

Public concern over the discharge of primarily treated sewage by two offshore outfalls in Mamala Bay, Oahu, prompted a multidisciplinary study to determine the impact of such activities on the water quality in the bay and at adjacent recreational beaches. As part of this study, we determined the abundance of coliphage as an indicator of fecal pollution along with total viral direct counts and phages infective for Vibrio parahaemoltyicus 16 at stations in Mamala Bay in four quarterly samplings over 13 months. Coliphage (< 1 to 1.2 x 10(3)/liter) were found during each quarterly sampling along an offshore transect to the Sand Island waste treatment facility outfall. The nonpoint coastal stations (Pearl Harbor, Ala Wai Canal, and Ke'ehi Lagoon) had high levels of coliphage during the storm event sampling in February 1994 but much lower levels or none when sampled during dry weather. Coliphage were absent at all samplings at Waikiki Beach and at the control station off Diamond Head. Viral direct counts in eutrophic coastal stations (Pearl Harbor, Ke'ehi Lagoon, Ala Moana Beach, and Ala Wai canal) averaged 10(9)/liter, while counts at offshore stations ranged from 9 x 10(7) to 1 x 10(9) viruses/liter, values similar to those for other marine environments. Vibriophage were found mainly in eutrophic coastal environments (Ala Wai Canal, Pearl Harbor, and Ke'ehi Lagoon) and at the Sand Island Transect stations D1 and D2. The greatest abundance was found during the storm event (February 1994) sampling. These results suggest that the Sand Island outfall influenced the water quality of the immediate surrounding waters but had little effect on the quality of the recreational beaches. Nonpoint discharge sources appeared to be more important in the distribution of fecal indicators in the coastal zone.     

Fish Community Structure on a Deep Ocean Outfall,Barber's Point,Oahu, Hawaii

The Barber's Point, Oahu, Hawaii sewer outfall structure attracts large numbers of fish (500 — 1000 per 336 m² bottom area) and fish species (23—29) not normally seen over flat, soft bottoms characteristic of the diffuser (66 m) isobath. Except for fish species strictly associated with corals, the adult fish community parameters (species richness, abundance, and composition) were similar to shallower natural Hawaiian reef environments. The adult fish species composition at the diffuser changed significantly during the discharge of heavy flocculated pre-treated sewage (15 mgd). High rates (15 mgd) of pre-treated sewage may cause decreases in total fish abundance and species richness when compared with the discharge of primary effluent with little or no flocculation between 0 and 19 mgd. Two fish species, which were generally abundant in Hawaiian waters during the years of observation, were absent at the outfall during discharge of heavy flocculated pre-treated effluent.     

Light- and nutrient-limited periphyton in low order streams of Oahu,Hawaii

To date, most studies of light- and nutrient-limited primary productivity in forested streams have been carried out in deciduous forests of temperate, continental regions. Conceptual models of light and nutrient limitation have been developed from these studies, but their restricted geographic range reduces the generality of such models. Unlike temperate continental streams, streams on tropical high islands are characterized by flashy, unpredictable discharge and riparian canopies that do not vary seasonally. These contrasting conditions suggest that patterns of light and nutrient limitation in tropical streams may differ from those in temperate streams. The effects of light, and nitrogen and phosphorus availability on periphyton accrual (measured as chlorophyll a per unit area) were investigated using field experiments in 4 low-order streams on the island of Oahu, Hawaii. Levels of chlorophyll a in partially-shaded stream pools were significantly greater than in heavily-shaded pools, and nutrient-enrichment increased the level of chlorophyll a in partially-shaded pools but not in heavily-shaded pools. In each stream, phosphate enrichment resulted in an increase in the level of chlorophyll a, but nitrate enrichment had no effect. Spates following rainstorms occur frequently in these streams, and may increase periphyton productivity by increasing the flux of nutrients to algal cells. However, differences in inorganic nitrogen and phosphorus concentrations measured during spates and baseflow were small, and during some spates, concentrations of these two nutrients declined relative to baseflow concentrations. These observations suggest that phosphorus limitation was not alleviated by spates.     

Age and composition of carbonate shoreface sediments, Kailua Bay, Oahu, Hawaii

The origin, age, and dynamics of carbonate sediments in Kailua Bay on Oahu, Hawaii, are described. The shoreface (from shoreline to 4 km offshore) consists of a broad (5 km²) fringing coral reef ecosystem bisected by a sinuous, shore-normal, sand-filled paleostream channel 200–300 m wide. The median grain diameter of surface sands is finest on the beach face (<0.3 mm) and increases offshore along the channel axis. Kailua sands are >90% biogenic carbonate, dominated by skeletal fragments of coralline algae (e.g. Porolithon, up to 50%) followed by the calcareous green alga Halimeda (up to 32%), coral fragments (1–24%), mollusc fragments (6–21%), and benthic foraminifera (1–10%). Sand composition and age across the shoreface are correlated to carbonate production. Corals and coralline algae, principal builders of the reef framework, are younger and more abundant in sands along the channel axis and in offshore reefal areas, while Halimeda, molluscs, and foraminifera are younger and more dominant in nearshore waters shoreward of the main region of framework building. Shoreface sediments are relatively old. Of 20 calibrated radiocarbon dates on skeletal constituents of sand, only three are younger than 500 years b.p.; six are 500–1000 years b.p.; six are 1000–2000 years b.p.; and five are 2000–5000 years b.p. Dated fine sands are older than medium to coarse sands and hence may constitute a reservoir of fossil carbonate that is distributed over the entire shoreface. Dominance of fossiliferous sand indicates long storage times for carbonate grains, which tend to decrease in size with age, such that the entire period of relative sea-level inundation (∼5000 years) is represented in the sediment. Despite an apparently healthy modern coral ecosystem, the surficial sand pool of Kailua Bay is dominated by sand reflecting an antecedent system, possibly one that existed under a +1–2 m sea-level high stand during the mid- to late Holocene. Accepted: 20 December 1999     

Trends in Sheltering and Welfare at the Hawaiian Humane Society,Oahu, Hawaii

One of the major goals of an animal welfare organization is to reduce the number of homeless, nonhuman animals in a community. In Hawaii, the Hawaiian Humane Society has provided numerous animal welfare services to work toward this goal, such as offering sterilizations and microchipping at reduced rates and facilitating animal adoptions and education. In addition, the Leash Law and the Cat Identification Program have increased animal welfare through increasing the responsibilities of companion animal caregivers (owners). The goal of this research was to assess if temporal changes in animal sheltering have occurred in Hawaii. The study assessed this by analyzing historical data on dogs (Canis familiaris) and cats (Felis catus) admitted, returned to owner, sterilized, euthanized, and adopted from the Humane Societies of Oahu, Hawaii, from 1993 to 2008. The study also analyzed dog and cat admittance and Honolulu population growth from 1975 to 2008. Sterilizations and pets returned to owners have increased significantly, whereas admittance and euthanasia rates have decreased significantly. Thus, although these data cannot conclusively state that there are fewer homeless animals in Hawaii, the results provide positive indicators of reducing homeless pets, especially when coupled with an increase in both the human population of Honolulu County and dog ownership.     

Trends in sheltering and welfare at the Hawaiian Humane Society, Oahu, Hawaii

One of the major goals of an animal welfare organization is to reduce the number of homeless, nonhuman animals in a community. In Hawaii, the Hawaiian Humane Society has provided numerous animal welfare services to work toward this goal, such as offering sterilizations and microchipping at reduced rates and facilitating animal adoptions and education. In addition, the Leash Law and the Cat Identification Program have increased animal welfare through increasing the responsibilities of companion animal caregivers (owners). The goal of this research was to assess if temporal changes in animal sheltering have occurred in Hawaii. The study assessed this by analyzing historical data on dogs (Canis familiaris) and cats (Felis catus) admitted, returned to owner, sterilized, euthanized, and adopted from the Humane Societies of Oahu, Hawaii, from 1993 to 2008. The study also analyzed dog and cat admittance and Honolulu population growth from 1975 to 2008. Sterilizations and pets returned to owners have increased significantly, whereas admittance and euthanasia rates have decreased significantly. Thus, although these data cannot conclusively state that there are fewer homeless animals in Hawaii, the results provide positive indicators of reducing homeless pets, especially when coupled with an increase in both the human population of Honolulu County and dog ownership.     

Characterization of Marine Temperate Phage-Host Systems Isolated from Mamala Bay, Oahu, Hawaii

To understand the ecological and genetic role of viruses in the marine environment, it is critical to know the infectivity of viruses and the types of interactions that occur between marine viruses and their hosts. We isolated four marine phages from turbid plaques by using four indigenous bacterial hosts obtained from concentrated water samples from Mamala Bay, Oahu, Hawaii. Two of the rod-shaped bacterial hosts were identified as Sphingomonas paucimobilis and Flavobacterium sp. All of the phage isolates were tailed phages and contained double-stranded DNA. Two of the phage isolates had morphologies typical of the family Siphoviridae, while the other two belonged to the families Myoviridae and Podoviridae. The head diameters of these viruses ranged from 47 to 70.7 nm, and the tail lengths ranged from 12 to 146 nm. The burst sizes ranged from 7.8 to 240 phage/bacterial cell, and the genome sizes, as determined by restriction digestion, ranged from 36 to 112 kb. The members of the Siphoviridae, T-HSIC, and T-D0, and the member of the Myoviridae, T-D1B, were found to form lysogenic associations with their bacterial hosts, which were isolated from the same water samples. Hybridization of phage T-HSIC probe with lysogenic host genomic DNA was observed in dot blot hybridization experiments, indicating that prophage T-HSIC was integrated within the host genome. These phage-host systems are available for use in studies of marine lysogeny and transduction.     

Anthropogenic Disturbance on Shallow Cryptofaunal Communities in a Marine Life Conservation District on Oahu,Hawaii

Cryptic invertebrate communities in coral rubble and sand from Hanauma Bay, a Marine Life Conservation District, were analyzed. Substratum samples were collected from the shallow bench and sand channels next to the beach and the cryptofauna were examined. Sand from the shallows (0.6 m deep) is frequently trampled by beach users and has a depauperate community dominated by a polychaete (Saccocirrus alanhongi) and a variety of nematodes (mean no. taxa = 12, mean no. individuals = 1,143 (0.1 m^–2), but sand collected 25 m seaward from below trampling depths (3 m). showed significantly greater diversity (mean no. taxa = 46, mean no. individuals = 6,448 (0.1 m^–2). Coralline rubble from 0.5 m depth was acid dissolved to extract the cryptofauna that was trapped on 0.5 and 0.25 mm sieves. In total, 102 taxa and 10,673 individual invertebrates (0.1 m^–2) were found. Rubble collected from areas used by waders had a greater diversity than sand habitats. This substratum provides a greater variety of microhabitats and protection from trampling for endolithic fauna than sand. Waders may actively avoid rubble because of the discomfort from walking on this hard, uneven substratum. We found that despite enforced protective measures, i.e., stopping fishing and collecting of marine life, banning fish feeding, and limiting the number of visitors, disturbance by human trampling on shallow sands still reduces the species richness in these areas. Cryptic biota below wading depths, and from adjacent coral rubble on sand, are not similarly affected. These results are similar to those from another heavily used beach on Oahu and cryptofauna ecology may be useful to adopt as a management option for Marine Preserves in other locations. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The Impacts of Introduced Poeciliid Fish and Odonata on the Endemic Megalagrion (Odonata) Damselflies of Oahu Island, Hawaii

Since the beginning of this century there have been substantial declines in the distribution and abundance of native Megalagrion damselflies on the Hawaiian Island of Oahu. Native damselflies have also vanished from most low elevation areas on other Hawaiian Islands, although historically, lotic and wetland dwelling damselfly species were once common throughout the archipelago. It is hypothesized that poeciliid fish introduced for biological control have caused the decline of four stream-breeding damselfly species on Oahu, and the extinction or near-extinction of two other species in Hawaii. This study documents the presence of remnant Megalagrion populations in Oahu streams, wetlands and estuaries, and records the elevational distributions of introduced fish in each waterbody surveyed. The distributions of introduced Odonata are also recorded, because the seven species of damselflies and dragonflies introduced to Oahu since 1936 present another potential threat to native Hawaiian damselflies. Native damselfly and introduced poeciliid fish distributions were mutually exclusive on Oahu, and it is concluded that this is probably due to predation by the introduced fish. By contrast, even the rarest native Megalagrion damselflies were found in areas containing introduced damselflies and dragonflies.     

Phylogeny and fitness of Vibrio fischeri from the light organs of Euprymna scolopes in two Oahu,Hawaii populations

The evolutionary relationship among Vibrio fischeri isolates obtained from the light organs of Euprymna scolopes collected around Oahu, Hawaii, were examined in this study. Phylogenetic reconstructions based on a concatenation of fragments of four housekeeping loci (recA, mdh, katA, pyrC) identified one monophyletic group (‘Group-A'') of V. fischeri from Oahu. Group-A V. fischeri strains could also be identified by a single DNA fingerprint type. V. fischeri strains with this fingerprint type had been observed to be at a significantly higher abundance than other strains in the light organs of adult squid collected from Maunalua Bay, Oahu, in 2005. We hypothesized that these previous observations might be related to a growth/survival advantage of the Group-A strains in the Maunalua Bay environments. Competition experiments between Group-A strains and non-Group-A strains demonstrated an advantage of the former in colonizing juvenile Maunalua Bay hosts. Growth and survival assays in Maunalua Bay seawater microcosms revealed a reduced fitness of Group-A strains relative to non-Group-A strains. From these results, we hypothesize that there may exist trade-offs between growth in the light organ and in seawater environments for local V. fischeri strains from Oahu. Alternatively, Group-A V. fischeri may represent an example of rapid, evolutionarily significant, specialization of a horizontally transmitted symbiont to a local host population.     

Population Structure of Vibrio fischeri within the Light Organs of Euprymna scolopes Squid from Two Oahu (Hawaii) Populations

We resolved the intraspecific diversity of Vibrio fischeri, the bioluminescent symbiont of the Hawaiian sepiolid squid Euprymna scolopes, at two previously unexplored morphological and geographical scales. These scales ranged from submillimeter regions within the host light organ to the several kilometers encompassing two host populations around Oahu. To facilitate this effort, we employed both novel and standard genetic and phenotypic assays of light-organ symbiont populations. A V. fischeri-specific fingerprinting method and five phenotypic assays were used to gauge the genetic richness of V. fischeri populations; these methods confirmed that the symbiont population present in each adult host's light organ is polyclonal. Upon statistical analysis of these genetic and phenotypic population data, we concluded that the characteristics of symbiotic populations were more similar within individual host populations than between the two distinct Oahu populations of E. scolopes, providing evidence that local geographic symbiont population structure exists. Finally, to better understand the genesis of symbiont diversity within host light organs, the process of symbiosis initiation in newly hatched juvenile squid was examined both experimentally and by mathematical modeling. We concluded that, after the juvenile hatches, only one or two cells of V. fischeri enter each of six internal epithelium-lined crypts present in the developing light organ. We hypothesize that the expansion of different, crypt-segregated, clonal populations creates the polyclonal adult light-organ population structure observed in this study. The stability of the luminous-bacterium-sepiolid squid mutualism in the presence of a polyclonal symbiont population structure is discussed in the context of contemporary evolutionary theory.