Abundance of small individuals influences the effectiveness of processing techniques for deep-sea nematodes

Nematodes are the most abundant metazoans of deep-sea benthic communities, but knowledge of their distribution is limited relative to larger organisms. Whilst some aspects of nematode processing techniques, such as extraction, have been extensively studied, other key elements have attracted little attention. We compared the effect of (1) mesh size (63, 45, and 32 μm) on estimates of nematode abundance, biomass, and body size, and (2) microscope magnification (50 and 100×) on estimates of nematode abundance at bathyal sites (250-3100 m water depth) on the Challenger Plateau and Chatham Rise, south-west Pacific Ocean. Variation in the effectiveness of these techniques was assessed in relation to nematode body size and environmental parameters (water depth, sediment organic matter content, %silt/clay, and chloroplastic pigments). The 63-μm mesh retained a relatively low proportion of total nematode abundance (mean ±SD = 55 ±9%), but most of nematode biomass (90 ± 4%). The proportion of nematode abundance retained on the 45-μm mesh in surface (0-1 cm) and subsurface (1-5 cm) sediment was significantly correlated (P < 0.01) with %silt/clay (R² = 0.39) and chloroplastic pigments (R² = 0.29), respectively. Variation in median nematode body weight showed similar trends, but relationships between mean nematode body weight and environmental parameters were either relatively weak (subsurface sediment) or not significant (surface sediment). Using a low magnification led to significantly lower (on average by 43%) nematode abundance estimates relative to high magnification (P < 0.001), and the magnitude of this difference was significantly correlated (P < 0.05) with total nematode abundance (R²p = 0.53) and the number of small (≤ 250 μm length) individuals (R²p = 0.05). Our results suggest that organic matter input and sediment characteristics influence the abundance of small nematodes in bathyal communities. The abundance of small individuals can, in turn, influence abundance estimates obtained using different mesh sizes and microscope magnifications

The effects of multiple trap spacing, baffles and brine volume on sediment trap collection efficiency

The hydrodynamic effects on trapping efficiency of sediment trap cross-frame position, baffles and brine volume were evaluated in three short-term (\u3c1 week) experiments in a temperate shallow marine environment (Evans Bay, Wellington Harbour, New Zealand). The effects of trap position and brine were further investigated during two open ocean, free-floating sediment trap deployments (1-2 days) near the Subtropical Front (STF), east of New Zealand. In the Evans Bay experiments (numbered I-III), cross-frames, each holding 12 cylindrical traps (inside diameter 9 cm, height 95 cm), were moored 3 meters above the seafloor in 15-18 m water depths at three randomly selected inner harbor sites. Triplicate subsamples from each cylinder were analyzed for total dry weight and mass fluxes calculated. The STF deployments utilized JGOFS MULTI-traps (inside diameter 7 cm, height 58 cm) attached to cross-frames moored at three depths (120, 300 and 550 m) on drifting arrays (Experiments IV and V). MULTI-trap samples were analyzed for total particulate mass, carbon and nitrogen. Results from Experiments I and V indicate that a spacing of about 3-trap diameters was sufficient to minimize inter-trap interactions and maintain trapping efficiency among traps suspended on a cross-frame at the same depth. Furthermore, baffles had no effect on trapping efficiency and an undetectable impact on zooplankton swimmer populations also collected in traps (Experiment II). In Experiment III, traps that were filled completely with high-density salt brine (50‰ excess NaCl) collected 2-3 times less material than traps with a basal brine height equivalent to 1- and 2.5-trap diameters. In contrast, high levels of inter-site variability confounded the STF MULTI-trap deployments during Experiment IV. However, variability in flux measurements from both Experiments III and IV increased 2 to 3-fold in brine-filled traps. Thus, the potential for brine-filled traps to undercollect material with higher levels of variability could possibly explain previously reported inaccuracies in the sediment trap method

Images of Swazi women living with HIV

Abstract Swaziland has one of the highest HIV prevalence rates in the world and a society marked by gender inequality. HIV positive women are therefore a marginalized and stigmatised group. This research explores the therapeutic potential of art for a group of nine Swazi women living with HIV. It is a qualitative exploratory study of a group’s experience and the artwork produced by them. The images made within the art group were examined in order to discover what they communicate about the women’s lives and what effect the image-making process has on the participants. An eclectic approach was adopted with concepts from art therapy theory, especially psychoanalytic, analytic, feminist and group art therapy, informing both the methodology and the analysis of the artwork created. The art work reveals how the dominant ideologies concerning motherhood, HIV and poverty inform the women’s identities. The image-making process was found to be therapeutic in that it provided a useful way for these women to explore their identity, trauma and assess their future goals. The social value of the group was clearly evident. The art group was presented as a practical strategy which can be used to give marginalized woman a voice. In my own practical work I explore the physical manifestation of AIDS deaths in the natural environment through the genre of landscape painting. My paintings are a witness to my empirical experience of the pandemic. A brief discussion of the concepts of the “uncanny”, “The Sublime” and palimpsest in paintings by Paul Nash, Caspar David Fredrich, Paul Cezanne, William Kentridge and Anselm Kiefer are used to establish a conceptual framework to understand my work

Insignificant enhancement of export flux in the highly productive subtropical front, east of New Zealand: a high resolution study of particle export fluxes based on Th-234: U-238 disequilibria

We evaluated the export fluxes of Particulate Organic Carbon (POC) in the Subtropical Frontal zone (STF) of the SW Pacific sector of the Southern Ocean. The site is characterized by enhanced primary productivity, which has been suggested to be stimulated through so-called natural iron fertilization processes where iron-depleted subantarctic water (SAW) mixes with mesotrophic, iron-replete subtropical water (STW). We adopted the small-volume Th-234 method to achieve the highest possible spatial sampling resolution in austral late autumn-early winter, May-June, 2008. Inventories of chlorophyll-a, particulate Th-234 and POC observed in the upper 100 m were all elevated in the mid-salinity water type (34.5 34.8) salinity waters which were of STW origin with low macronutrients. However, Steady-State Th-234 fluxes were similar across the salinity gradient being, 25 +/- 0.78 ((1.5 +/- 0.047) x 10(3)) in the mid-salinity, and 29 +/- 0.53 ((1.8 +/- 0.032) x 10(3)) and 22 +/- 1.1 Bq m(-2) d(-1) ((1.3 +/- 0.066) x 10(3) dpm m(-2) d(-1)) in the high and low salinity waters respectively. Bottle POC/Th ratios at the depth of 100 m were used to convert Th-234 fluxes into POC export fluxes. The derived POC flux did not appear to be enhanced in mid-salinity waters where the primary productivity was inferred to be the highest at the time of sampling, with a flux of 11 +/- 0.45 mmol C m(-2) d(-1), compared to 14 +/- 0.39 mmol C m(-2) d(-1) in high salinity waters and 8.5 +/- 0.66 mmol C m(-2) d(-1) in low salinity waters. This study thus implied that natural iron fertilization does not necessarily lead to an enhancement of POC export in STF regions

Coccolithophore biodiversity controls carbonate export in the Southern Ocean

Southern Ocean waters are projected to undergo profound changes in their physical and chemical properties in the coming decades. Coccolithophore blooms in the Southern Ocean are thought to account for a major fraction of the global marine calcium carbonate (CaCO3) production and export to the deep sea. Therefore, changes in the composition and abundance of Southern Ocean coccolithophore populations are likely to alter the marine carbon cycle, with feedbacks to the rate of global climate change. However, the contribution of coccolithophores to CaCO3 export in the Southern Ocean is uncertain, particularly in the circumpolar subantarctic zone that represents about half of the areal extent of the Southern Ocean and where coccolithophores are most abundant. Here, we present measurements of annual CaCO3 flux and quantitatively partition them amongst coccolithophore species and heterotrophic calcifiers at two sites representative of a large portion of the subantarctic zone. We find that coccolithophores account for a major fraction of the annual CaCO3 export, with the highest contributions in waters with low algal biomass accumulations. Notably, our analysis reveals that although Emiliania huxleyi is an important vector for CaCO3 export to the deep sea, less abundant but larger species account for most of the annual coccolithophore CaCO3 flux. This observation contrasts with the generally accepted notion that high particulate inorganic carbon accumulations during the austral summer in the subantarctic Southern Ocean are mainly caused by E. huxleyi blooms. It appears likely that the climate-induced migration of oceanic fronts will initially result in the poleward expansion of large coccolithophore species increasing CaCO3 production. However, subantarctic coccolithophore populations will eventually diminish as acidification overwhelms those changes. Overall, our analysis emphasizes the need for species-centred studies to improve our ability to project future changes in phytoplankton communities and their influence on marine biogeochemical cycles.info:eu-repo/semantics/publishedVersio

Seasonal Cycles of Phytoplankton and Net Primary Production from Biogeochemical Argo Float Data in the South-West Pacific Ocean

We present annual cycles of chlorophyll a, phytoplankton carbon, nitrate and oxygen for Subtropical (STW), Subantarctic (SAW), and Subantarctic Mode (SAMW) waters near Aotearoa New Zealand from data collected by two Biogeochemical (BGC) Argo floats. We develop two simple models of depth-integrated net primary production (NPP), tuned against 14C-uptake measurements, to compare with Vertically-Generalised Production Model (VGPM) satellite-based estimates of NPP. One model is the simplest possible, and assumes production is proportional to light multiplied by chlorophyll a concentration. The second model modifies the light response profile to account for photoacclimation. In STW at 30–35°S, enhanced production is initiated in austral autumn when the mixed layer deepens to entrain nutrients into the photic zone. For about half the year, there is substantial production within a deep chlorophyll maximum that sits below the mixed layer. Consequently, depth-integrated NPP is only loosely related to surface biomass as imaged from satellite remote-sensing, and BGC Argo-based model estimates of depth-integrated NPP are about double VGPM estimates. In SAW at 45–55°S, production is initiated when vertical mixing decreases in austral spring. Production is largely within the mixed layer, and depth-integrated phytoplankton biomass and depth-integrated NPP follow surface phytoplankton biomass. Model estimates of depth-integrated NPP based on BGC Argo float profiles are comparable with VGPM estimates for the southern water masses

Emerging from the third space chrysalis: Experiences in a non-hierarchical, collaborative research community of practice

This article discusses the creation of a research-focused virtual community of practice (vCoP) for geographically-dispersed third space professionals, motivated by desires for enhanced professional collaboration, visibility and identity. The authors used collaborative autoethnography (CAE) to evaluate their personal reflections as vCoP participants. Data were gathered in two collaborative writing activities and analysed using thematic analysis (TA). The TA identified two connected themes, which capture the vCoP members’ aspirations to transcend their current roles and be research-active through connecting with like-minded professionals. Collaborative writing activities, including authoring this paper, cultivated elements of academic identity such as independence and purpose. A non-hierarchical and supportive vCoP environment allowed the members to work beyond time and institutional constraints to foster the evolution of the community and an emerging sense of professional identity beyond that typically associated with third space roles. The paper offers a model of collaboration that could help groups in similar situations

Working together: reflections on a non-hierarchical approach to collaborative writing

The process of writing is a cornerstone for academia, reflecting values such as rigour, critique and engagement (Mountz et al., 2015). Academic writing is typically valorized as an individual endeavour, but with the advancement of technology such as synchronous online writing platforms, opportunities to construct scholarly knowledge collaboratively have multiplied (Nykopp et al., 2019). Collaborative writing (CW) involves ‘sharing the responsibility for and the ownership of the entire text produced’ (Storch, 2019, 40), factors that have certainly been enhanced by developing technologies. CW differs from cooperative writing, which involves a division of labour with each individual being assigned to, or completing, a discrete sub-task (Storch, 2019). This chapter discusses the reflections of ten authors from a UK-based research virtual Community of Practice (vCoP) on the challenges and positives encountered during the CW of a research journal article using a shared Google Document

Why are biotic iron pools uniform across high- and low-iron pelagic ecosystems?

Dissolved iron supply is pivotal in setting global phytoplankton productivity and pelagic ecosystem structure. However, most studies of the role of iron have focussed on carbon biogeochemistry within pelagic ecosystems, with less effort to quantify the iron biogeochemical cycle. Here we compare mixed-layer biotic iron inventories from a low-iron (~0.06nmol L-1) subantarctic (FeCycle study) and a seasonally high-iron (~0.6nmol L-1) subtropical (FeCycle II study) site. Both studies were quasi-Lagrangian, and had multi-day occupation, common sampling protocols, and indirect estimates of biotic iron (from a limited range of available published biovolume/carbon/iron quotas). Biotic iron pools were comparable (~100±30pmol L-1) for low- and high-iron waters, despite a tenfold difference in dissolved iron concentrations. Consistency in biotic iron inventories (~80±24pmol L-1, largely estimated using a limited range of available quotas) was also conspicuous for three Southern Ocean polar sites. Insights into the extent to which uniformity in biotic iron inventories was driven by the need to apply common iron quotas obtained from laboratory cultures were provided from FeCycle II. The observed twofold to threefold range of iron quotas during the evolution of FeCycle II subtropical bloom was much less than reported from laboratory monocultures. Furthermore, the iron recycling efficiency varied by fourfold during FeCycle II, increasing as stocks of new iron were depleted, suggesting that quotas and iron recycling efficiencies together set biotic iron pools. Hence, site-specific differences in iron recycling efficiencies (which provide 20-50% and 90% of total iron supply in high- and low-iron waters, respectively) help offset the differences in new iron inputs between low- and high-iron sites. Future parameterization of iron in biogeochemical models must focus on the drivers of biotic iron inventories, including the differing iron requirements of the resident biota, and the subsequent fate (retention/export/recycling) of the biotic iron

Collaborative writing communities for Learning Development research and practice

This workshop discussed how collaborative reflection and writing provides us, as a group of Learning Developers, with insights into our role and sense of identity. The wider potential for using collaborative writing to develop topics of mutual interest was also explored. Our reflections on the collaborative writing process arose from our first-hand experience of collaborative writing (Bickle et al., 2021). Therefore, we aimed to introduce participants to the tools we used for our writing and encourage them to experience the tools themselves to stimulate a discussion on the potential and challenges of collaborative writing for LD research and practice. We hoped to increase participants’ understanding of collaborative writing through practice and reflection and provide ideas on how others can initiate a collaborative writing community. The introduction briefly outlined the insights we gained from our study, focussing particularly on the way collaborative writing served as a tool to examine and broaden our identities as Learning Developers. It also introduced the methodologies for creating (collaborative writing) and analysing (collaborative autoethnography) data. Next, participants were invited to try out collaborative writing activities and reflect on their potential use as part of their own practice. We used a Google document (Figure 1) to collect their spontaneous responses to short writing prompts related to the challenges and potential of collaborative writing. Finally, at the end of the session, participants left with tips and techniques on how to develop a collaborative writing group of their own