Stephen R. Wing

HAGFISH IN THE NEW ZEALAND FJORDS ARE SUPPORTED BY CHEMOAUTOTROPHY OF FOREST CARBON

Forest litter is often considered to be a minor energy source to marine communities due to its refractory nature. Large volumes of forest litter are deposited in the New Zealand fjords, and likely recycled into available energy by microbial activity. In this study we used evidence from stable isotope analyses to test whether recycled carbon from chemoautotrophs was an important contributor to the diet of hagfish (Eptatretus cirrhatus). We then analyzed fatty acid biomarkers from the chemoautotrophic clam Solemya parkinsoni and E. cirrhatus to further discriminate the contribution of marine, terrestrial, and chemoautotrophic sources. Bulk isotopic signatures of E. cirrhatus varied considerably (delta13C, from -29.2 per thousand to -16.7 per thousand; delta15N, from -2.8 per thousand to +15.5 per thousand; delta34S, from -21.7 per thousand to +16.7 per thousand) and indicated that a significant percentage of organic matter (38-51%) originated from chemoautotrophs (delta13C, -31.3 per thousand +/- 0.1 per thousand [mean +/- SE]; delta15N, -5.7 per thousand +/- 0.2 per thousand; delta34S, -32.per thousand +/- 3.8 per thousand). Fatty acid biomarkers were depleted in 13C, particularly cis-vaccenic acid (18:1omega7: delta13C, -39.0 per thousand) indicating specific microbial origins of carbon. A high proportion of forest litter in sediments, coupled with isotopic and fatty acid biomarker results, indicates that terrestrial organic matter is a dominant contributor to this marine benthic system. This study demonstrates a clear linkage between terrestrial and marine ecological processes.

Inter-annual variability in larval supply to populations of three invertebrate taxa in the northern California Current

Abstract We investigated sources of inter-annual variability in larval supply to crab and sea urchin populations at Bodega Head and Point Reyes in northern California. During the spring and summer upwelling seasons of the years 1992 through 1997 we monitored the weekly settlement rates of nine species of crabs and two species of sea urchins. As observed in previous studies, daily values of alongshore windstress, temperature and salinity provided evidence for the poleward flow of relatively warm, low salinity water from south of Point Reyes, an apparent retention zone, during upwelling relaxation events. In years dominated by these events (1992, 1993, 1995 and 1996) we observed that alongshore windstress, temperature and salinity were coherent and temperature was significantly correlated with cancrid crab settlement. During these years the magnitude of cancrid crab settlement and the fraction of cancrid crabs relative to other crab species settling were high. Over four years of concurrent sampling there was consistently greater cancrid crab settlement at the Point Reyes site, within the retention zone, than at Bodega Head. Settlement of non-cancrid crabs (porcellanids, grapsids, pagurids and majids) was not as closely linked to intra-annual patterns of upwelling and relaxation, possibly due to the shorter seasonal availability of larvae allowing for the influence of fewer relaxation events. Settlement of this group among years was positively correlated with environmental indicators of strong seasonal upwelling; high salinity, Bakun upwelling index and low temperature. Sea urchin settlement events were observed in June and July of 1992, 1994 and 1997 during warming periods when salinity and temperature were increasing and alongshore windstress was low. Across the six years of the study, we found that cancrid crab larvae had a more even seasonal availability than larvae of non-cancrid species, which settled in greatest numbers during the early portion of the upwelling season. Sea urchins settled in greatest numbers during the later part of the upwelling season. Together these patterns demonstrate the taxon-specific way that inter-annual variability in larval supply is forced by the coincidence of larval availability with favorable physical transport mechanisms.

Calorific content of New Zealand marine macrophytes

Abstract Calorific content was measured in 28 species of New Zealand macroalgae. Values ranged from 1.04 to 3.34 kcal g‐1 dry weight (wt), 3.03–5.18 kcal g‐1 ash‐free dry wt, and 0.13–1.75 kcal g‐1 wet wt. Seasonal variation in calorific content was measured in two of these species, Macrocystis pyrifera and Ulva lactuca, both of which showed clear changes in energy content over a 1‐year period. Factors affecting variation in calorific content between species and during the year are discussed, and the application of the current findings to ecological and aquacultural research on New Zealand seaweeds are considered.

Reproductive sources and sinks within a sea urchin, Evechinus chloroticus, population of a New Zealand fjord

We examined population structure of New Zealand sea urchins Evechinus chloroticus across the Doubtful-Thompson Sound complex, a fjord with a large influx of freshwater, a low salin- ity surface layer and a mean estuarine circulation. Measurements of abundance, growth, gonad development and larval settlement were collected at 9 sites. We observed large differences in each of these vital population parameters among sites. The highest growth rates and gamete production occurred at the entrances of the fjord. We used 3 alternative growth models to test whether the spa- tial pattern in growth rates was robust. Variability in growth among sites likely reflected differences in nutritional history, as indicated by the Aristotles lantern index. Size distributions taken 2 yr apart at each of the 9 sites showed that the adult mode was relatively stable in time. As a consequence much of the variance in mean size among sites could be explained by differences in growth rather than in mortality or recruitment. The highest abundance and aggregation of sea urchins occurred at mid-fjord and entrance sites, which coincided with the highest rates of larval settlement and sug- gested limited larval supply elsewhere. The observed spatial patterns in vital rates were used to eval- uate the likely influences of spatial heterogeneity in larval production on larval dispersal patterns within the fjord, based on particle movements within a validated hydrodynamic model. We then tested the sensitivity of these model results to magnitude of wind and rainfall events and duration of larval development. Results from our field observations and modeling studies suggest that the sea urchin population in Doubtful-Thompson Sound is likely composed of distinct areas of reproductive source and sink.

Reproduction of the sea urchin Evechinus chloroticus (Echinodermata: Echinoidea) in a New Zealand fiord

Abstract The reproductive cycle of Evechinus chloroticus (Val.) was examined at three (outer, mid, and inner) sites in Doubtful Sound, Fiordland over a 3‐year period. We found that sea urchins from all three populations had an annual gametogenic cycle, the timing of which was temporally and spatially consistent. Inter‐individual variation in the gametogenic cycle was noted within each population, however, initiation of gametogenesis was generally synchronous among males and females and among sites, occurring in May/June. Strong asynchrony in gamete maturation was observed in Deep Cove, occurring in males 4–5 months earlier than females. Spawning occurred in December at the inner and mid fiord sites, while occurring in January at the outer fiord site. Reproductive potential (maximum gonad index) and output (weight of gametes released/g of animal/year) varied spatially and temporally, where there was a consistent decreasing trend in reproductive potential and output with increasing distance away from the fiord entrance. Spatial variation in reproductive output may be associated, in part, with the strong ecological gradient found in Doubtful Sound, where there is a reported decrease in macrophyte biomass and cover towards the fiord headwaters. The implications of spatial differences in gonad production with respect to the population biology and fisheries management of E. chloroticus in the fiords are discussed.

HISTORICAL EVIDENCE FOR HABITAT CONVERSION AND LOCAL POPULATION DECLINE IN A NEW ZEALAND FJORD

Although direct links between habitat conversion and human activities are often apparent, their causal mechanisms may be less obvious. We identified historic salinity change, attributed to freshwater input from a hydroelectric power plant, as a potential mechanism of intertidal habitat conversion and severe local decline of the New Zealand littleneck clam (Austrovenus stutchburyi) in Doubtful Sound, New Zealand. Live clams were abundant at sites distant from the power plant with relatively unaltered salinity regimes, and were absent from the inner fjord near the power plant outflow. Remnant shells indicate past habitation by A. stutchburyi at inner fjord sites. Historic salinity conditions inferred from oxygen isotope ratios in shell carbonates confirm that salinity previously reached higher values in the inner fjord, and that A. stutchburyi probably has not inhabited that area since salinity was at pre-power-plant levels. A laboratory experiment showed that A. stutchburyi from Doubtful Sound have a high tolerance for low salinity conditions, but that hyposaline conditions become lethal after extended exposure (37-day LC50 = 2.5). In situ transplant experiments demonstrated that present salinity conditions in the inner reaches of Doubtful Sound are lethal to this species. Our findings suggest that the increased fresh- water input maintained by the power plant has converted the habitat in the inner reaches of Doubtful Sound to one with sustained low salinity unsuitable for the survival of A. stutchburyi.

Sea ice microbial production supports Ross Sea benthic communities: influence of a small but stable subsidy

Diversity in guilds of primary producers enhances temporal stability in provision of organic matter to consumers. In the Antarctic ecosystem, where temporal variability in phytoplankton production is high, sea ice contains a diatom and microbial community (SIMCO) that represents a pool of organic matter that is seasonally more consistent, although of relatively small magnitude. The fate of organic material produced by SIMCO in Antarctica is largely unknown but may represent an important link between sea ice dynamics and secondary production in nearshore food webs. We used whole tissue and compound-specific stable isotope analysis of consumers to test whether the sea ice microbial community is an important source of organic matter supporting nearshore communities in the Ross Sea. We found distinct gradients in delta13C and delta15N of SIMCO corresponding to differences in inorganic carbon and nitrogen acquisition among sites with different sea ice extent and persistence. Mass balance analysis of a suite of consumers demonstrated large fluxes of SIMCO into the nearshore food web, ranging from 5% to 100% of organic matter supplied to benthic species, and 0-10% of organic matter to upper water column or pelagic inhabitants. A delta13C analysis of nine fatty acids including two key biomarkers for diatoms, eicosapentaenoic acid (EPA, 20:5omega3), and docosahexaenoic acid (DHA, 22:6omega3), confirmed these patterns. We observed clear patterns in delta13C of fatty acids that are enriched in 13C for species that acquire a large fraction of their nutrition from SIMCO. These data demonstrate the key role of SIMCO in ecosystem functioning in Antarctica and strong linkages between sea ice extent and nearshore secondary productivity. While SIMCO provides a stabilizing subsidy of organic matter, changes to sea ice coverage associated with climate change would directly affect secondary production and stability of benthic food webs in Antarctica.

Photoacclimation of Ecklonia radiata (Laminariales, Heterokontophyta) in Doubtful Sound, Fjordland, Southern New Zealand

S. M. Miller, S. R. Wing and C. L. Hurd. 2006. Photoacclimation of Ecklonia radiata (Laminariales, Heterokontophyta) in Doubtful Sound, Fjordland, Southern New Zealand. Phycologia 45: 44–52. DOI: 10.2216/04-98.1 The kelp Ecklonia radiata is found in the sublittoral zone in the Doubtful Sound complex, and is most abundant at the coastal entrance with abundance declining toward the head of the Sound. A feature of the fjord is a persistent tannin-stained, low-salinity layer (LSL) on the surface of the underlying salt water. In this unique marine environment there is an inverse relationship between the thickness of the LSL and light levels – at the head of Doubtful Sound the LSL is thicker and light reaching E. radiata at depth can be extremely low; the inverse occurs at the coastal entrance. The mountainous terrain reduces light further, particularly on the northern aspect of the fjord. To assess whether E. radiata showed evidence of photoacclimation across this light gradient, sporophytes were collected from five sites within the complex in November 2000. Pigment contents [chlorophyll (chl) a, c and fucoxanthin], photosynthetic parameters [maximum photosynthetic rate (Pmax), alpha (α), respiration rate (Rd), saturation photon-flux density (PFD) (Ek), compensation PFD (Ec) and photoinhibition (β)] and morphological parameters of E. radiata were measured. Results indicate that E. radiata acclimates to the low light at sites near the head of the fjord by increasing pigment contents, particularly chl a, as well as the surface area of the thallus. Furthermore, E. radiata increases its efficiency at capturing and transferring energy at low light by increasing α and decreasing Ek and Ec values. In doing so, E. radiata maintains similar dry weight–normalized Pmax at the five sites. It is suggested that photoacclimation may therefore be a process by which E. radiata overcomes the reduced light imposed by the LSL and extends its distribution towards the inner reaches of the fjord.

Evidence for discrete subpopulations of sea perch (Helicolenus ercoides) across four fjords in Fiordland, New Zealand

Abstract In coastal populations of invertebrates and fishes, the distribution of discrete subpopulations is influenced by adult and larval dispersal, as well as by the effects of habitat heterogeneity on site fidelity or connectivity. Here, we examine evidence for spatial structure of sea perch, Helicolenus percoides, populations among four fjords in the Fiordland region of southwestern New Zealand. We examine patterns in adult morphology, length-at-age, δ13C and δ15N of muscle tissue, and trace elemental composition of whole otoliths as proxies for population isolation among the four inner fjord regions. A multivariate analysis of morphometrics reveals significant differences among populations from each of the four sites, suggesting existence of four distinct subpopulations. These patterns are consistent with observed differences in δ13C and δ15N, and length-at-age estimates among the four subpopulations. Differences in whole otolith concentrations of Sr, Ba, Mg and Li, and high classification scores based on the whole otolith elemental fingerprint are also consistent with significant subdivision among areas. Patterns across all four markers are consistent with discrete subpopulation structure of adult sea perch among the four study sites. These data indicate that the newly implemented network of marine protected areas in Fiordland is likely to contain discrete populations of sea perch.

Fiordland: the ecological basis for ecosystem management

Marine ecosystems are structured by physical and biological influences on: production and transport of organic matter; population dynamics; and food web architecture. Here, we review how scientific insights in the Fiordland marine area have supported ecosystem management. Fiordland is a case study for four ecological paradigms: 1. physical forcing of productivity; 2. subsidies of organic matter; 3. reproductive source-sink dynamics; and 4. stability of food web architecture. Understanding of these processes underpinned development of a network of marine reserves comprising the first regional experiment in marine ecosystem management for New Zealand. Monitoring the marine reserves demonstrated increasing abundance of rock lobsters (Jasus edwardsii) and blue cod (Parapercis colias). Further, analyses of reef fish communities indicated reserves supported abundant high trophic level omnivores, leading to stable communities and intact food webs. These results demonstrated success in two of the objectives of ecosystem management–enhanced production of exploited species and preservation of biodiversity.