Rice Bay Research Articles

Producing rice while conserving the habitat of an endangered waterbird: Incentives for farmers to integrate water management

Effective incentive programs for farmers to conserve biodiversity on their properties are vital for sustainability. Most such programs have focussed on natural areas, like revegetating waterways, but novel agricultural habitats amplify the commitment required of farmers and the need for collaboration in the conservation process. The rice fields of Australia’s Murray-Darling Basin are a key habitat for a globally endangered waterbird, the Australasian bittern, but early and sufficient ponding periods that facilitate successful breeding are inconsistent with maximising yield per megalitre of water used. We aimed to understand farmers’ willingness to undertake ‘bittern-friendly’ rice growing practices and their preferences for hypothetical incentive programs. Public recognition of the habitat values of their fields was a key motivation for participation, and, across the industry, we estimated that rice growers were willing to forgo an annual profit margin totalling $AU1.42 million per annum to further bittern conservation. We tested for social desirability bias, finding the inferred valuation – their nearest rice growing neighbour – was 51 % lower, but still a substantial in-kind contribution. More than half of growers did not need compensation to control foxes and cats, or to avoid herbicide use on rice bay banks, while about a third would undertake each of the other conservation actions. For financial incentives, a choice experiment showed the payment rate was important but farmers strongly preferred less demanding management requirements. The 11-day variation in ponding commencement and period was highly valued by growers, and can be crucial to bitterns. Growers also preferred higher levels of contract flexibility, while the intensity of compliance monitoring had little impact on their choices. The preferred incentive type was to use public environmental water with no money exchanged, followed by a consumer-funded program with bittern-friendly rice products, and a standard government contract, whereas a pledge system and a tender were relatively unpopular. Bittern-friendly rice growing incentive programs should be successful if they foster custodianship, harness in-kind contributions, improve rice farming’s public image, and work with growers where opportunity costs for additional water are low.

The Stellate Burrow: A Large and Complex Trace Fossil in Holocene Carbonate Eolianites of the Bahamas

abstractLarge, complex burrows, informally referred to as stellate burrows, are present in eolianites of windward sea-cliff exposures facing Exuma Sound on Moriah Harbour Cay (Exumas, Bahamas). These cliffs consist of limestones (age <1,800 years before present) assigned to the Hanna Bay Member of the Rice Bay Formation and comprise three progradational lithofacies of foreshore, backshore, and dune deposits. Upper foreshore and backshore beds contain well-preserved specimens of Psilonichnus upsilon, fossil burrows of the ghost crab Ocypode quadrata. The overlying eolianites exhibit typical physical sedimentary structures characteristic of coastal dunes, with the most striking feature being the abundant presence of stellate burrows consisting of a central shaft (∼3 to 7 cm diameter) and numerous upward-directed branches (∼1 cm diameter) with smooth, unlined walls that form a radiate pattern in cross section. Parallel central shafts commonly join at the base, forming distinctive U-shaped structures that reach total heights of >1 m. Other examples exhibit an irregular arrangement of shafts that merge to form exceptionally large and architecturally complex structures. The result is a distinctive ichnofabric reaching levels of 3 or more on the Droser-Bottjer Ichnofabric Index scale. The presence of abundant stellate burrows can result in a significant increase in porosity and permeability within host eolianites. Previously, stellate burrows were assigned to the ichnogenus Cellicalichnus, with origin attributed to burrowing and brooding activity of halictid (sweat) bees, common today in the Bahamas. Nonetheless, diagnostic cell structures are not present, and there are other important differences between stellate burrows and the previously described ichnospecies of Cellicalichnus. Other tracemaker possibilities are considered and evaluated, but firm identification of the tracemaker for the stellate burrows remains to be resolved.

Lipid biomarkers in ooids from different locations and ages: evidence for a common bacterial flora

Ooids are one of the common constituents of ancient carbonate rocks, yet the role that microbial communities may or may not play in their formation remains unresolved. To search for evidence of microbial activity in modern and Holocene ooids, samples collected from intertidal waters, beaches and outcrops in the Bahamas and in Shark Bay in Western Australia were examined for their contents of lipid biomarkers. Modern samples from Cat and Andros islands in the Bahamas and from Carbla Beach in Hamelin Pool, Western Australia, showed abundant and notably similar distributions of hydrocarbons, fatty acids (FAs) and alcohols. A large fraction of these lipids were bound into the carbonate matrix and only released on acid dissolution, which suggests that these lipids were being incorporated continuously during ooid growth. The distributions of hydrocarbons, and their disparate carbon isotopic signatures, were consistent with mixed input from cyanobacteria together with small and variable amounts of vascular plant leaf wax [C27 -C35 ; δ(13) C -25 to -32‰Vienna Pee Dee Belemnite (VPDB)]. The FAs comprised a complex mixture of C12 -C18 normal and branched short-chain compounds with the predominant straight-chain components attributable to bacteria and/or cyanobacteria. Branched FA, especially 10-MeC16 and 10-MeC17 , together with the prevalence of elemental sulfur in the extracts, indicate an origin from sulfate-reducing bacteria. The iso- and anteiso-FA were quite variable in their (13) C contents suggesting that they come from organisms with diverse physiologies. Hydrogen isotopic compositions provide further insight into this issue. FAs in each sample show disparate δD values consistent with inputs from autotrophs and heterotrophs. The most enigmatic lipid assemblage is an homologous series of long-chain (C24 -C32 ) FA with pronounced even carbon number preference. Typically, such long-chain FA are thought to come from land plant leaf wax, but in this case, their (13) C-enriched isotopic signatures compared to co-occurring n-alkanes (e.g., Hamelin Pool TLE FA C24 -C32 ; δ(13) C -20 to -24.2‰ VPDB; TLE n-alkanes δ(13) C -24.1 to -26.2 -‰VPDB) indicate a microbial origin, possibly sulfate-reducing bacteria. Lastly, we identified homohopanoic acid and bishomohopanol as the primary degradation products of bacterial hopanoids. The distributions of lipids isolated from Holocene oolites from the Rice Bay Formation of Cat Island, Bahamas were very similar to the beach ooids described above and, in total, these modern and fossil biomarker data lead us to hypothesize that ooids are colonized by a defined microbial community and that these microbes possibly mediate calcification.

Red Lionfish (Pterois volitans) Invade San Salvador, Bahamas: No Early Effects on Coral and Fish Communities

Biological invaders are a leading contributor to global losses of biodiversity. A recent invader to the waters surrounding San Salvador, Bahamas, the red lionfish, Pterois volitans, was first reported in 2006; by 2009 they were common in waters 2-40 m deep around the island. Our study collected data on coral communities and fish assemblages at three patch reef complexes (Rice Bay, Rocky Point, Lindsay Reef) in 2007, during the initial phase of the invasion, and compared the results to a nearly identical study done in 2001 before P. volitans colonized San Salvador. Prey selection and quantity of consumption by P. volitans were also examined. Coral and fish species richness, diversity, percent cover (corals) and abundance (fish) were similar in 2001 and 2007. Of the 5,078 fish recorded during our study on shallow patch reefs, only two were P. volitans, but they were more prevalent in deeper water along San Salvador’s “wall.” Captured P. volitans ranged in size from 19-32 cm, all longer than maturity length. Pallid goby (Coryphopterus eidolon), black cap basslet (Gramma melacara) and red night shrimp (Rynchocienetes rigens) were the most commonly identified stomach contents. The effects of the successful invasion and increasing population of P. volitans on San Salvador’s reef ecosystem are uncertain at this time; future monitoring of potential changes in coral and fish communities on the patch reefs of San Salvador is recommended to determine if population control measures need to be considered. Initial post-invasion data (2007), along with pre-invasion data (2001), are valuable benchmarks for future studies.

Testing cosmic dose rate models for ESR: Dating corals and molluscs on San Salvador, Bahamas

Sealevel curves are best developed on tectonically stable coastlines, like San Salvador, where eolianites preserve transgressive and regressive phases associated with Quaternary high seastands, while reef facies mark the highstands. At 11 locations around San Salvador, terrestrial molluscs ( Cerion ) from the eolianites, lagoonal bivalves ( Codakia ), and corals from the highstand deposits were dated by ESR. Volumetrically averaged sedimentary dose rates were calculated from sedimentary geochemistry and time-averaged cosmic dose rates from each sample’s current and past geologic contexts. Rice Bay Formation corals dated at 3.9 ± 0.3 to 7.1 ± 0.4 ka (OIS 1). Minimum ages for the Cockburn Town Member’s regressive phase ranged from 49 ± 6 to 75 ± 8 ka, correlating with OIS 3–4. Codakia dates showed that an OIS 5a sealevel approached modern levels at 91–78 ka. In situ corals from the Cockburn Town Reef averaged from 127 ± 6 to 138 ± 10 ka, correlating well with OIS 5e. Ages from the Reef’s rubble zones hint that some coral reefs grew as early as OIS 7, but were likely reworked during OIS 5. San Salvador preserves deposits from three mid to late Quaternary highstands above, and as many as three that closely approach, modern sealevel.

Morphological abnormalities in frogs from a rice-growing region in NSW, Australia, with investigations into pesticide exposure

Three frog species (Limnodynastes tasmaniensis, Limnodynastes fletcheri and Litoria raniformis) were surveyed in rice bays of the Coleambally Irrigation Area (CIA), NSW, Australia, during the rice-growing seasons of 2005/2006 and 2006/2007. A total external morphological abnormality index of 7.0% was observed in frogs of the CIA (n=1,209). The types and frequencies of abnormalities were typical of reports from agricultural areas with ectrodactyly being the most common aberration. A relatively low abnormality index of 1.2% was observed in L. raniformis (n=87) compared to indices of 7.1% and 8.2% observed in L. fletcheri (n=694) and L. tasmaniensis (n=428), respectively. No conclusive evidence was found of unnaturally high rates of intersex, gonadal maldevelopment or unbalanced sex ratios in any species. Rice bay surface waters differed significantly in mean pesticide concentrations of atrazine and metolachlor on farms growing rice and corn compared to farms with rice as the sole crop. However, the similar abnormality indices observed in recent metamorphs emerging from these two farm types provided no evidence to suggest a link between larval exposure to the measured pesticides and developmental malformations.

Emplacement and deformation features of syntectonic leucocratic veins from Rainy Lake zone (Western Superior Province, Canada)

Networks of leucocratic veins are widespread in the Rice Bay–Redgut Bay domain of the Rainy Lake zone at the Wabigoon–Quetico subprovince boundary (Archean Superior Province, Canada). Vein geometries and their cross-cutting relationships with host rocks are indicative of syntectonic emplacement within a regional late Archean transpressional deformation event (Kenoran orogeny). The relative folding and boudinage of the veins compared to their host rocks indicate that they were emplaced syntectonically with the D 2 deformation. Semi-quantitative strain and vorticity analyses confirm the syn-D 2 timing of the veins. The observed structural features are interpreted as being formed during magma emplacement along dilatant fractures and subsequent solid-state deformation under overall ductile deformation conditions. The structures related to emplacement are better preserved in domains of low post-emplacement strain and veins intruded into competent host rocks, whereas the folds and boudins related to post-emplacement deformation are well developed in veins intruded into relatively incompetent host rocks. In domains of high strain, the primary intrusive structures are modified or even locally obliterated due to increasing deformation. It is envisaged that regional kinematics and the rheological state of host rocks are the main controls on the style of vein emplacement and deformation. The variety of observed structures is considered the result of deformation and lithological heterogeneity rather than several distinct magmatic events.

Simulating the fate of molinate in rice paddies using the RICEWQ model

The contamination of drainage channels and creeks with pesticides used in the production of rice is of concern in south eastern Australia. Of major concern is the molinate that at times has been detected in over 25% of water samples from surface drains and creeks. The objective of this study was to evaluate the rice pesticide model RICEWQ version 1.7.2 for its applicability in simulating the fate of the pesticide molinate in paddy rice floodwater in south eastern Australia. The model was successfully calibrated using water depths and molinate concentrations obtained from a rice bay. By using the calibrated model, the effects of the different application methods and the rates of molinate on water quality were investigated. The molinate, which was applied directly onto ponded water, led to higher maximum concentrations in the ponded water than for application onto a dry bay, which was subsequently filled. However, the concentrations in water declined more rapidly for the application onto a ponded bay than those for the application onto a dry bay. The simulation results suggest that water and chemical management has great effects on chemical concentration in the runoff water. Overall, the RICEWQ model accurately predicted the molinate concentrations in floodwater and this model can be used to develop best management practices in rice farming.

Sun Hats and Ichnofabrics: Fourth International Ichnofabric Workshop, San Salvador Island, Bahamas, March 15-22, 1997

Sun Hats and Ichnofabrics: Fourth International Ichnofabric Workshop, San Salvador Island, Bahamas, March 15-22, 1997

Geology and karst geomorphology of San Salvador Island, Bahamas

The exposed carbonates of the Bahamas consist of late Quaternary limestones that were deposited during glacio-eustatic highstands of sea level. Each highstand event produced transgressive-phase, stillstand-phase, and regressive-phase units. Because of slow platform subsidence, Pleistocene carbonates deposited on highstands prior to the last interglacial (oxygen isotope substage 5e, circa 125,000 years ago) are represented solely by eolianites. The Owl's Hole Formation comprises these eolianites, which are generally fossiliferous pelsparites. The deposits of the last interglacial form the Grotto Beach Formation, and contain a complete sequence of subtidal, intertidal, and eolian carbonates. These deposits are predominantly oolitic. Holocene deposits are represented by the Rice Bay Formation, which consists of intertidal and eolian pelsparites deposited during the transgressive-phase and stillstand-phase of the current sea-level highstand. The three formations are separated from one another by well-developed terra-rossa paleosols or other erosion surfaces that formed predominantly during intervening sea-level lowstands.

Methane mitigation in flooded Louisiana rice fields

A field experiment was conducted to determine whether selected nitrification inhibitors (encapsulated calcium carbide and dicyandiamide) and SO inf4 sup-2 -containing compounds [(NH4)2SO4 and Na2SO4] had mitigating effects on CH4 emissions from flooded rice. Microplots were established within a rice bay drill-seeded with the Texmont rice cultivar and CH4 fluxes were measured over the main rice cropping season. Methane emissions over the 77-day sampling period were approximately 230, 240, 260, 290, 310, and 360 kg CH4 ha-1 from the calcium carbide, Na2SO4-rate II, Na2SO4-rate I, (NH4)2SO4, dicyandiamide, and urea (control) treatments, respectively. Reductions in CH4 evolution, compared to the control, ranged from 14 to 35%, depending on treatment. The selected inhibitors and SO inf4 sup-2 -containing compounds appear to be effective in reducing the CH4 emitted from flooded rice fields.

Rice Bloodworm, Toxicity of Fatty Acids, 1981

Abstract The toxicities of solutions of saturated straight chain fatty acids and the potassium soaps of 2 of them to RB larvae were evaluated in the laboratory. Fatty acids with 1-8 and 10 carbon atoms were bioassayed at concentrations of 50, 10 and 1 mg/liter in distilled water. Additionally, solutions of formic, butyric, propionic and capric acids and the potassium soaps of the last 2 acids were made up in water collected from a 2 wk previously flooded rice bay. The pH of the solutions ranged from 5.0-5.5. Each treatment consisted of a 25 ml aliquot of fatty acid solution in 25 mm diameter glass tube and was replicated 4 times. Ten late instar RB larvae from a laboratory colony were placed in each tube, capped and held at 25°C ± 2°C and assessed for mortality after 24 h. Appropriate untreated controls were maintained for each assay and all treatment results were corrected for control mortality. Larvae were counted as dead if they failed to respond to a jet of water.

Mesoscale physical sedimentary structures and trace fossils in Holocene carbonate eolianites from San Salvador Island, Bahamas

Carbonate eolianites, less than 10,000 years old, are well exposed in sea cliffs and on rocky shore platforms along the northeast coast of San Salvador Island. These deposits formed when easterly trade winds blew carbonate sands landward from the beach zone as sea level rose over a previously exposed shelf during the Holocene transgression. Small, lobate, parabolic-like dunes coalesced laterally to form an elongate, transverse dune ridge oriented perpendicular to the prevailing wind direction. Detailed observations of small-scale sedimentary structures and laminations permit the distinction of sands deposited as climbing wind ripples, lee-side grainfalls, and lee-side sandflows. Micrite crusts and associated plant trace fossils characteristic of the dunal environment are common in the Rice Bay Formation, and these can be compared directly with identical features and plants found in modern carbonate dunes on San Salvador. Some eolian laminations dip into the present-day subtidal zone, confirming a post-depositional rise in sea level along this tectonically stable coast. The rocks are lithified sufficiently by freshwater, vadose, low Mg-calcite cement to form wave-resistant sea cliffs. A distinctive feature of these terrestrial carbonate rocks is the occurrence of a variety of animal trace fossils. Skolithos linearis burrows, up to 30 cm in length and 0.5 cm in diameter, are quite common. Comparison with traces found in modern carbonate dunes suggests that these trace fossils were made by burrowing insects or spiders. The most abundant and widespread trace fossil consists of closely spaced, irregular, small burrows up to 20 cm long in the horizontal plane and with uniform diameters of 0.3–0.4 cm. These burrows also extended downward as much as 3 cm into the sediments, and created a mottled texture in places. This trace fossil has been found only in lee-side sandflow and grainfall deposits. Such burrows probably were produced by insects or insect larvae, which favored the protected lee-side environment. The most unusual trace fossil in these Holocene eolianites is composed of a cluster of vertically oriented burrows. Each cluster consists of up to several hundred shafts, each with a diameter of 1–2 cm, that diverge upward from an approximately common point of origin. These structures can be 1.4 m or more high and greater than 1 m in transverse section across the circular shape produced by the upwardly radiating burrow cluster. These trace fossils probably represent the escape pathways of the hatchlings of an infaunal insect or similar invertebrate.

Poor growth of summer crops due to phosphate deficiency after rice cultivation—No involvement of soil-borne plant pathogens

Aerated steam treatment of drained rice soils at 60°, 80° and 100°C for 30 min had no significant effect on the dry matter production of maize seedlings indicating that soil-borne root disease micro-organisms are not involved in the poor growth of maize in these soils. No evidence of Mn or Fe toxicity was apparent in plant tissue analyses. The 100°C steam treatment significantly depressed the amount of phosphorus fertilizer required to provide an equilibrium P concentration in soil solutions of 0.13 μg ml −1 (P req) in both rice bank and bay soils. In bay soils this effect was also observed in 60° and 80°C treatments. Differences in concentrations of P REQ between bank and bay soils were detected in untreated and 60°C treated soils. These differences were no longer apparent at the two higher temperatures. The effect of increasing heat treatment on the P REQ of these soils was not reflected in the less sensitive Shukla single-value method for determining P sorptivity. Incorporation of sufficient P fertilizer to provide a minimum P concentration of 0.13 μg ml −1 in both rice bank and rice bay soils eliminated differences in seedling growth of maize in these soils. Poor phosphate availability was therefore confirmed as the major constraint on the growth of maize seedlings growing in drained rice soils.

Geology and geochemistry of the Rainy Lake Area

Abstract Major stratigraphic units in the Rainy Lake area include graywackes (Coutchiching), mafic and felsic volcanic rocks (Keewatin), and conglomerates and associated finer-grained clastic rocks (Seine), Tonalites (Laurentian) intruded the Coutchiching and Keewatin, and, following a period of folding, contributed clasts to the younger Seine sediments. Granitic plutosn (Algoman) were emplaced during a younger igneous and metamorphic event. Radiometric dating places all of the major rock-forming events between 2700 and 2600 Ma ago. Uplift and stabilization 26000 to 2400 Ma ago resulted in widespread retrograde metamorphism and local cataclasis. Compositional differences between the Coutchiching gneisses in Rice Bay and the lower grade graywackes in the Bears Passage belt reflect different source terranes. Major rock types in the Keewatin are massive and pillow basalts of tholeiitic composition, and felsic rhyodacites with quartz phenocrysts; intermediate rocks are uncommon. Gabbroic sills were emplaced in the Keewatin as the volcanic pile thickened, and anorthosite cumulates reflect differentiation of larger bodies of magma. Sills of leucotonalite and leucogranodiorite are abundant at Rice Bay as slightly discordant bodies in the Coutchiching gneisses and in the overlying Keewatin volcanic rocks. Laurentian intrusions are highly sheared and altered tonalites and granodiorites. Algoman intrusions are less deformed, elliptical-shaped plutons of granodiorite and quartz monzonite. The Ottertail Lake Pluton, the largest body, is zoned from biotite-hornblende granodiorite at the margin to leucocratic quartz monzonite at the center. Angular inclusions of Keewatin rocks are abundant at the margin. These decrease in size and angularity inward where they are last recognized as small mafic clots and schlieren in quartz monzonite. The diversity and general bimodal character of the major igneous rocks units have resulted from different source materials, degrees of melting, and the crustal history of the magmas — fractional crystallization and contamination. Keewatin volcanic rocks evolved through differentiation of tholeiitic magmas, and similarities between the rhyodacites and the Laurentian tonalites suggest that these may be related. Leucocratic sills abundant in Rice Bay are not genetically related to the Keewatin rocks but have some similarities to the Algoman rocks. Marked variations in the Ottertail Lake stock probably resulted from both contamination and differentiation. The origin of these magma is not clear but deviation from the same source as the Keewatin rocks is unlikely. With the development and thickening of the crust, a greater diversity of material became available for magmatic recycling.