Jellyfish Lake Research Articles

Marine lakes as biogeographical islands: a physical model for ecological dynamics in an insular marine lake, Palau

Marine lakes are emerging ecological and evolutionary natural experimental systems, with genetically isolated resident populations that exhibit extreme population dynamics and rapid phenotypic change. Marine lakes are posited to be marine islands, however, unlike terrestrial islands for which rich models have been developed over the past half-century, we know little of the mechanisms driving changes in marine lakes. This is a critical knowledge gap in efforts to reconcile theory on, or distinguish differences among, island and island-like systems. To reduce this critical knowledge gap, we present a mathematical model describing marine lakes based on a case study of Jellyfish Lake (Ongeim’l Tketau, Mecherchar: OTM), Palau. Empirical data show that marine lakes exhibit delayed and reduced tidal motions, suggesting exchange of a limited amount of water with the neighboring (‘mainland’) ocean. Our model tracks changes in lake level, allowing determination of an exchange rate that is a physical null model for biological colonization and a proxy for colonization distance in island biogeography theory. In addition, we track horizontally averaged in-lake quantities such as salinity and temperature (i.e., marine weather, climate) and stratification (i.e., habitat) — that are known to influence resident species’ distributions and population dynamics — by solving an advection-diffusion equation. We find that weather, ocean conditions, groundwater, and exchanges through tunnels determine the abiotic environment in OTM. By comparing simulations and data, we estimate the difficult-to-measure properties of the surrounding groundwater — the ‘matrix’ in the vernacular of habitat islands — and give a range of realistic values for the effective diffusion coefficient. This coefficient is found to increase in a tropical storm, suggesting that other drivers can be important during perturbations.

Recognizing peripheral ecosystems in marine protected areas: A case study of golden jellyfish lakes in Raja Ampat, Indonesia

Peripheral marine ecosystems can harbor endemic diversity and attract tourism attention, yet are generally not included in conservation management plans due to their remoteness or inland positioning. A case study in Raja Ampat of seven landlocked marine lakes containing golden jellyfish (Mastigias spp.) was conducted to address the lack of fundamental insights into evolutionary, ecological and social contexts of these ecosystems. An interdisciplinary approach was taken towards identifying the jellyfish lakes as distinct management units in order to incorporate them into existing Marine Protected Areas. Mastigias papua populations showed strong genetic (ϕST: 0.30–0.86) and morphological (F = 28.62, p-value = 0.001) structure among lakes, with putative new subspecies. Risks arising from rapid increase in tourism to Raja Ampat (30-fold since 2007) warrant restrictions on jellyfish lake use. Recommendations are provided for adaptive management and science-based conservation policies for jellyfish lakes across Indonesia.

Climatic, physical, and biogeochemical changes drive rapid oxygen loss and recovery in a marine ecosystem

Dissolved oxygen (DO) concentrations shape the biogeochemistry and ecological structure of aquatic ecosystems; as a result, understanding how and why DO varies in space and time is of fundamental importance. Using high-resolution, in situ DO time-series collected over the course of a year in a novel marine ecosystem (Jellyfish Lake, Palau), we show that DO declined throughout the marine lake and subsequently recovered in the upper water column. These shifts were accompanied by variations in water temperature and were correlated to changes in wind, precipitation, and especially sea surface height that occurred during the 2015–2016 El Niño-Southern Oscillation event. Multiple approaches used to calculate rates of community respiration, net community production, and gross primary production from DO changes showed that DO consumption and production did not accelerate nor collapse; instead, their variance increased during lake deoxygenation and recovery, and then stabilized. Spatial and temporal variations in rates were significantly related to climatic variability and changes in DO, and causality testing indicated that these relationships were both correlative and causative. Our data indicate that climatic, physical, and biogeochemical properties and processes collectively regulated DO, producing linked feedbacks that drove DO decline and recovery.

Expansion of an introduced sea anemone population, and its associations with native species in a tropical marine lake (Jellyfish Lake, Palau)

Understanding the full range of consequences of species introductions into island and marine habitats requires quantitative studies of systems that are currently under-represented in the scientific literature. We document the introduction, proliferation and establishment of a non-native sea anemone species in an isolated tropical marine lake, a marine ‘island’. From 2003–2012, we gathered samples to identify the introduced species and used transect and photo-quadrat surveys to describe its abundance, distribution, and any associations with native species or habitats. The non-native sea anemone was first found at the tourist entry into the lake in 2003 and identified as Exaiptasia pallida (Agassiz 1864), a species with zooxanthellae endosymbionts. Temporal patterns of tourism, the spatial extent of the sea anemone in 2003, and genetic analyses of the symbiont were consistent with the early stages of introduction. Subsequent expansion of E. pallida throughout the lake occurred within six years. The native species assemblages that were invaded by E. pallida were heterogeneous among surveys and habitats. Overall, there were few correlations that were significant between percent cover of E. pallida and native species; most significant associations were negative; the majority were on mangrove roots. There was one positive association between E. pallida and a native sponge. No significant relationship was found between the abundance of E. pallida and native species diversity. The rapid expansion of E. pallida but dearth of strong ecosystem effects presents a case study of invasive species in a tropical marine habitat where consequences are not directly proportional to invasive abundance. Whether this outcome is stable and representative of other species introduced into marine lakes, or elsewhere in marine systems, remains to be seen.

Jellyfish distribution and abundance in relation to the physical habitat of Jellyfish Lake, Palau

Abstract:Animals often select for habitats that increase their chance of survival by balancing the need to acquire food, reproduce and avoid predation. Perennial blooms of golden jellyfish (Mastigias papua etpisoni) are present in Jellyfish Lake, Palau, a popular tourist destination. Based on the species’ economic importance and unusual behavioural complexity, increased understanding of jellyfish habitat selection is necessary. We used a novel approach, a REMUS autonomous underwater vehicle, to quantify jellyfish distribution, abundance and habitat, and compared these findings to traditional methods. Midday acoustic surveys showed jellyfish distribution was patchy and the population resided mainly on the eastern side of the lake, as it is known that jellyfish migrate eastward towards the sun. Highest vertical densities of jellyfish were at 6–7 m, potentially to mitigate UV damage or photoinhibition of their photosymbionts, suggesting a coupling exists between their vertical distribution and water properties. Abundance estimates of jellyfish were ~2.75 and ~7.1 million (~2 million excluding bell diameters <1 cm) from acoustic and net samples, suggesting the methodology employed underestimated the population's smaller size fraction and non-synoptic surveys could impact estimates due to unresolved patchiness. Our approach could investigate population dynamics, behaviour or habitat associations on fine scales.

Mixed medusivory by the sea anemone Entacmaea medusivora (Anthozoa: Actiniaria) in Kakaban Lake, Indonesia

Anchialine lakes are landlocked marine water bodies, which may contain swarms of scyphozoan jellyfish (Becking et al. 2011). Because most jellyfish are pelagic, published examples of their predation by sessile benthic organisms are rare and, in the case of anthozoan predators, only single prey species have been clearly documented (Fautin and Fitt 1991; Jarms and Tiemann 2004; Alamaru et al. 2009). Two anchialine lakes are known to contain the medusivorous sea anemone Entacmaea medusivora Fautin and Fitt 1991: Jellyfish Lake in Palau (Fautin and Fitt 1991) andKakaban Lake in East Kalimantan, Indonesia (Tomascik and Mah 1994). In Palau, this species preys on Mastigias papua (Lesson, 1830) (Fautin and Fitt 1991). During surveys of Kakaban Lake (02°08′27′′N, 118°30′40′′ E) in October 2003 and August 2008, medusivory by E. medusivora was observed at <3 m depth. Sea anemones occurred on substrates consisting of green alga, Halimeda sp. (Fig. 1a, b), logs, and mangrove roots. Three species of jellyfish acted as prey: Mastigias papua (Fig. 1c, d), Aurelia aurita (Linnaeus, 1758) (Fig. 1e, f), and Cassiopeia ornata Haeckel 1880 (Fig. 1g, h). This study is the first to present in situ photographic evidence of a benthic anthozoan species predating on more than one species of Scyphozoa. Experiments have

Pyramidodinium atrofuscum gen. et sp. nov. (Dinophyceae), a new marine sand-dwelling coccoid dinoflagellate from tropical waters

SUMMARY A new marine sand-dwelling coccoid dinoflagellate Pyramidodinium atrofuscum Horiguchi et Sukigara gen. et sp. nov. is described from Jellyfish Lake, Republic of Palau. The dinoflagellate alternates a non-motile vegetative stage with a motile gymnodinioid stage within its life cycle. The non-motile stage is dominant in the life cycle and the dinoflagellate reproduces itself by means of the production of two motile cells. The released motile cell swims only for a short period and is directly transformed into the non-motile cell. The non-motile cell is sessile, pyramidal in shape, with a single longitudinal ridge and a double transverse ridge. The surface of the cell wall is covered with many processes. The motile cell has a Gymnodinium-like morphology, but no apical groove is present. An ultrastructural study revealed that the dinoflagellate possesses typical dinoflagellate organelles. Based on the unique morphology of the vegetative non-motile stage, we propose a new genus Pyramidodinium for this dinoflagellate, with the type species Pyramidodinium atrofuscum Horiguchi et Sukigara, gen. et sp. nov.

Enrichment of Excess 210Po in Anoxic Ponds

We have investigated the cycling of naturally occurring 210Po in waters from seasonally anoxic Pond B (South Carolina) and permanently anoxic Jellyfish Lake (Palau Islands, western Pacific Ocean). The maximum 210Po activity in Pond B was about 14 mBq L(-1) during summer. This activity was much higher than its parent 210Pb activity, indicating excess 210Po inputs from bottom sediments. The summertime excess 210Po activity was accompanied by increases in Fe and Mn, suggesting 210Po diffusion from bottom sediments under reducing conditions. Activity of 210Po was much lower underwinter oxic conditions, most likely a consequence of efficient coprecipitation with Fe and Mn oxides that occurs with destruction of Pond B stratification. In permanently anoxic Jellyfish Lake, the maximum activity of 210Po was 133 mBq L(-1), among the highest reported from any surface aqueous environment. A box model suggests that the release of only 2% of 210Po, produced from the 210Pb in the bottom sediments, would account for the observed excess. Our results suggest that 210Po can be naturally enriched in anoxic environments to a high level, perhaps in concert with the Fe and Mn redox cycles.

ACAROTROCHUS LOBULATUS, A NEW GENUS AND SPECIES OF SHALLOW-WATER BENTHIC FORAMINIFER FROM MECHERCHAR JELLYFISH LAKE, PALAU, NW EQUATORIAL PACIFIC OCEAN

Acarotrochus lobulatus, a new species of shallow-water calcareous benthic foraminifer, was found in core material from the meromictic Mecherchar Jellyfish Lake of Palau, northwestern equatorial Pacific. The species belongs to a new genus, Acarotrochus, which is assigned to the Family Discorbidae Ehrenberg, 1838. The principal characters of Acarotrochus are a low trochospiral test with a foramenal plate of an extension of septal flap dividing a main chamber lumen and foliar chamberlet, a deeply incised umbilical intraseptal interlocular space which is half-covered by the backward extension of the folium, and the foliar aperture opening at the peripheral end of the foliar chamber. This new species has been found only in the calcareous layer in the core investigated, where the age is estimated to be ~100 years B.P. (end of the Little Ice Age). It may have since been extirpated from the lake.

Simplified synthesis of an 8-hydroxyquinoline chelating resin and a study of trace metal profiles from Jellyfish Lake, Palau

Abstract We report a simplified synthesis, and some performance characteristics, for 8-hydroxyquinoline (8-HOQ) covalently bonded to a chemically resistant TosoHaas TSK vinyl polymer resin. The resin was used to concentrate trace metals from stored, acidified seawater samples collected from Jellyfish Lake, an anoxic marine lake in the Palau Islands. The Mn, Fe, and Zn profiles determined from the 8-HOQ resin extraction were similar to those determined using Chelex-100 resin. The Zn and Cd profiles did not exhibit removal by sulfide “stripping” in contrast to other anoxic marine basins. The profiles of Co and Ni also exhibited elevated concentrations in the anoxic hypolimnion. The solution speciation and saturation states for the metals were calculated using revised metal-bisulfide stability constants. The calculations suggest that the MS(HS)− species dominates the solution speciation for Mn, Co, Ni, Zn, Cd, and Pb. Cu(I) is modeled as the CuS− or Cu(HS)2− species, while Fe(II) behaves as the free Fe2+ cation. The Mn, Co, Ni, Cu and Cd concentrations appeared to be at least 10-fold undersaturated, while the Fe(II), Zn, and Pb concentrations were close to saturation with respect to their metal sulfides.

Benthic Foraminifera from the Meromictic Mecherchar Jellyfish Lake, Palau (Western Pacific)

Foraminifera occur in the peculiar, meromictic Jellyfish Lake on Mecherchar Island in the Palau Archipelago (Western Caroline Islands). The lake is marine, 30 m deep, and characterized by both oxic and anoxic water layers separated by a distinct chemo-and thermocline. Above 15 m, the lake is well lighted, oxic, and with normal marine salinity and temperatures. Below that, the lake is dark and anoxic with high sulfide content in the water and sediment. Sediment surface samples, collected by SCUBA from sites within both layers, contain few foraminifera. The foraminiferal fauna is characterized by a particularly low-diversity and thin-shelled assemblage and is devoid of typical diverse reef and lagoonal species commonly present in South Pacific reef complexes, including those surrounding Mecherchar Island just 100 m or so from Jellyfish Lake. A total of 15 species was recovered from surface sediments in the upper oxic zone of the lake, but no foraminifera were found in those samples collected in the deeper, anoxic water of the lake. Two species, Helenina sp. and Ammonia sp., dominate in the shallow-water lake habitats (0-10 m), while the agglutinated species Glomospira fijiensis and Rheophax scorpiurus appear to be most tolerant to decreasing oxygen conditions at the anoxic/oxic interface. The foraminiferal faunal association most closely resembles assemblages that have been described from mangrove environments of the South Pacific. The specific distribution pattern and the absence of foraminifera within the anoxic zone is consistent with findings from volcanic sulfide-rich environments. The physico-chemical properties of this stratified lake, in particular the lack of dissolved oxygen and the high concentration of hydrogen sulfide within the anoxic water layer, appear to control this particular presence/absence pattern of benthic foraminifera.

Jellyfish Lake, Palau: Regeneration of C, N, Si, and P in anoxic marine lake sediments

Sediment cores from Jellyfish Lake were processed under an inert atmosphere and the pore waters extracted and analyzed for the following parameters: pH, titration alkalinity (TA), Cl−, H4SiO4, PO43−, NH4+, Ca2+, Mg2+, SO42−, and H2S. Additionally, in one set of pore‐water samples (core 10), the δ13C of the ∑CO2 was also determined. The TA, H4SiO4, PO43−, NH4+, and H2S increased with depth in the pore waters above anoxic bottom‐water values. H2S values increased to 3.8 M. In one case, both H4SiO4 and PO43− concentrations increased to a maximum value and then decreased with depth, suggesting removal into solid phases. The H4SiO4 concentrations are equal to or greater than pore‐water value observed in sediments underlying upwelling areas. PO43− concentrations are, in general, lower than pore‐water values from terrigenous nearshore areas but higher than nearshore carbonate pore‐water values from Florida Bay or Bermuda. The Ca2+, Cl−, and Mg2+ : Cl− ratios show slight decreases in the top 15–20 cm, suggesting that authigenic carbonate may be forming. This suggestion is supported by the fact that the pore waters are saturated with respect to CaCO3 due to the very high TAs. The δ13C measurements of the pore‐water ∑CO2 are from a shorter core. These measurements reach their most negative concentration at 72 cm and then become slightly heavier. This change is accompanied by a decrease in TA, suggesting the onset of methanogenesis at this location in this core.

Speciation and isotopic composition of sulfur in sediments from Jellyfish Lake, Palau

Jellyfish Lake, Palau, is a meromictic marine lake with high organic productivity, low reactive Fe content, and anoxic bottom waters. Sediment samples from Jellyfish Lake were examined for the distribution of sulfur species and their isotopic signatures in order to gain a better understanding of sedimentary sulfur incorporation in Fe-poor environments. Surface samples were taken along a transect from a near-shore site to the center of the lake, and include a sample below oxic water, a sample below the chemocline layer, and samples below anoxic waters. Three additional samples were taken from a core, 2 m long, collected near the lake center. Sulfur to organic carbon weight ratios in all samples were lower than the expected value of 0.36 for normal marine sediment, probably because the lake water is deficient in reactive Fe to form iron sulfides. Total sulfur contents in the surface sediments indicated no changes with distance from shore; however, the sulfur content of the surface sample at the chemocline layer may be slightly higher. Total sulfur content increased with depth in the core and is inversely related to organic carbon content. Organic sulfur is the major sulfur species in the samples, followed in descending order by sulfate, disulfides and monosulfides. Sulfate sulfur isotope δ 34S-values are positive (from +20.56 to +12.04‰), reflecting the marine source of sulfate in Jellyfish Lake. Disulfide and monosulfide δ 34S-values are negative (from −25.07 to −7.60‰), because of fractionation during bacterial reduction of sulfate. Monosulfide δ 34S-values are somewhat higher than those of disulfides, and they are close to the δ 34S-values of organic sulfur. These results indicate that most of the organic sulfur is formed by reaction of bacteriogenic monosulfides, or possibly monosulfide-derived polysulfides, with organic matter in the sediment.

Microbial characteristics of Palau Jellyfish Lake

Microbiological examinations of total bacterial population, culturable aerobic heterotrophs, photosynthetic bacteria, and particulate DNA were carried out in Palau Jellyfish Lake. A 2 m thick bacterial plate layer at 13–15 m depth consisting of various components of microbes was observed in Jellyfish Lake. Photosynthetic bacteria, as seen by flow cytometry, were concentrated at 14–15 m depths with a maximal count of 2.2 × 105 cells∙mL−1 and microscopic analysis confirmed that these purple bacteria were Chromatium sp. Peaks in total bacterial counts (8.3 × 106 cells∙mL−1; 13 m), in the Synechococcus spp. population (2.4 × 106 cells∙mL−1; 13 m), in culturable heterotrophs (105 colony-forming units∙mL−1; 15 m), and in particulate DNA (17.8 μg∙L−1; 10 m) were observed either at the bacterial plate layer that was rich in nutrients or just above this layer in the oxic zone. Bacteriochlorophyll and chlorophyll a exhibited peaks at the photosynthetic bacterial plate (14–15 m). A high concentration of particulate organic carbon was also observed at 15 m. The particulate DNA showed a high degree of correlation with the total bacterial cell number. A low ratio of particulate DNA to particulate organic carbon (0.005) in the water column was found at 15 m and suggested that the particulate materials produced by photosynthetic bacteria would have influenced the concentration of particulate organic carbon. Culturable heterotrophs, clustered into nine different groups, were dominated by species of the genera Vibrio, Aeromonas, and Halomonas.Key words: Jellyfish Lake, microbiological characteristics, Chromatium, particulate DNA, heterotrophs.

Jellyfish Lake, Palau: Early diagenesis of organic matter in sediments of an anoxic marine lake

Jellyfish Lake, a meromictic, marine lake in the Palau Islands, western Pacific Ocean, is accumulating organic matter‐rich sediments (46% wt/wt) below anoxic, highly sulfidic bottom water. Elemental and stable isotope (δ13C) data indicate that the sedimentary organic matter is primarily derived from vascular plant remains (65–90%) and would form a type 2 kerogen. A bacterial layer at the oxic‐anoxic interface in the water column may play an important role in the rapid recycling of algal‐derived organic matter from the highly productive surface waters.The major postdepositional change in the sedimentary organic matter is carbohydrate biodegradation, as shown by 13C NMR. Lignin and aliphatic substances are preserved in the sediments. Dissolved organic matter in pore waters is primarily composed of carbohydrates, reflecting the degradation of sedimentary carbohydrates. Rate constants for organic carbon degradation and sulfate reduction in sediments of the lake are about 10 × lower than in other anoxic sediments. This may reflect the vascular plant source and partly degraded nature of the organic matter reaching the sediments of the lake.Elemental results from sediment cores and stable isotope (δ18O, δ13C) studies of shells from the sediments indicate probable climatic or ecological fluctuations affecting the depositional environment of the lake between 80 and 110 yr ago. The high sedimentation rate and stable environment of Jellyfish Lake make it a possible environment for studies of climatic fluctuations during the Holocene.

Nutrient cycling and the biogeochemistry of manganese, iron. and zinc in Jellyfish Lake, Palau

The oxic waters in Jellyfish Lake, a stagnant marine lake in Palau, are depleted in NO3−, PO43−, dissolved Si, Mn, Fe, and Zn, while the underlying anoxic waters are significantly enriched in these species and NH3. NH3 and PO43 regeneration and dissolved sulfide production in the anoxic zone yield a stoichiometry of C138N13P for organic matter undergoing recycling in the anoxic waters. In the anoxic zone, dissolved Mn, Fe, and Zn reach maximum concentrations of 30, 22, and 2.5 nM. The Fe concentrations are consistent with mackinawite or greigite solubility control. Mn approaches saturation with respect to haurite. Zn may be controlled by the solubility of ZnS coprecipitate. The sediments are enriched in Fe and depleted in Zn relative to Asian dust at Enewetak. A two-box model is used to calculate an eddy diffusion coefficient of 0.0015 cm2 s−1 across the chemocline. The upward diffusive loss of NH3 added to the sedimentation rate of N and multiplied by the stoichiometric C : N ratio yields an organic carbon flux into the anoxic waters of 1,200 µmol C cm−2 yr−1, which is ∼ 13% of the total primary productivity.

Jellyfish Lake, Palau

Elemental cycling in suboxic to anoxic marine environments has received considerable attention in the past few years. The recent expeditions of the RIV Knorr to the Black Sea, for example, illustrate the interest in deciphering the geochemical processes active in such environments “Murray, 1988”.This interest has been stimulated by the recognition that the type of elemental cycling that occurs in restrictive basins such as the Black Sea also occurs in many other environments. Examples include hydrothermal systems, estuarine and marine sediments, and other water columns with restrictive circulation. In addition, evidence that widespread anoxia has occurred in oceans of the geologic past “Fischer and Arthur, 1977; Jenkyns, 1980” requires us to obtain a better understanding of geochemical processes under such conditions. We report here on preliminary geochemical measurements made in a stratified marine lake—an unusual, yet useful environment as an analog of an anoxic ocean.

Dissolved inorganic nitrogen flux in symbiotic and nonsymbiotic medusae1

Symbiotic Mastigias from Eil Malk Jellyfish Lake and Palau lagoon take up and retain ammonium during both day and night. Uptake is due to symbiotic dinoflagellates (zooxanthellae). Nitrate is not taken up, and is barely detectable in the environment. Nonsymbiotic Aurelia in the same lake excrete rather than take up ammonium. Mastigias migrates vertically repeatedly at night, periodically visiting the nutrient‐rich chemocline at about 15 m where, together with that taken up at ambient concentrations, the animals may take up enough ammonium to satisfy the total daily nitrogen requirement of their symbiotic algae. These observations are consistent with the hypothesis that repeated vertical migration by Mastigias is a behavioral adaptation in the animal that facilitates nutrient acquisition by its algal symbionts.

The physical, chemical, and biological characteristics of a stratified, saline, sulfide lake in Palau1

Eil Malk Jellyfish Lake in Palau is a 5‐ha, 30‐m deep, meromictic saline lake, stratified, with anoxic hypolimnion, damped, delayed tides, and no heat accumulation. The top 15 m are oxygenated, nutrient‐poor but turbid, with high primary productivity and large planktonic populations of only five metazoans: the medusae Mastigias and Aurelia, the copepods Oithona and Acrocalanus, and silverside fish, Pranesus. At the chemocline a floating bacterial plate dominated by photosynthetic purple bacteria (Chromatium) degrades and solubilizes almost all particulate material and absorbs all sunlight. Below the plate the anoxic, clear water contains extremely high levels of NH4+, H2S, and PO43−. Sediments are primarily undisturbed fish fecal pellets full of copepod exoskeletons. The lake is stable, aseasonal, and shows no obvious cycles of the populations. An unusual horizontal and vertical swimming behavior of Mastigias appears related to light and to the nutrient requirements of its symbiotic zooxanthellae. Other zooplankton show normal vertical diurnal migration patterns. Facultafive schooling by Pranesus reflects the absence of predators in the lake.