Trends In Primary Production Research Articles

Assessing vulnerability of reptile hotspots through temporal trends of global change factors in the Iberian Peninsula

Habitat degradation and climate change are major threats to the long-term persistence of reptile populations. However, their roles on primary productivity instability remain unclear at certain scales. Besides, the design of protected areas has often overlooked reptiles or assumed that their ecological requirements are represented under the umbrella of more charismatic species. Here, we assess the vulnerability of areas of high diversity of reptiles in the Iberian Peninsula to global change using data from satellite imagery. We focused on primary productivity, climate and land-use change because they are indicators of environmental variability that might impair ecosystem functioning and alter wildlife communities. We used linear regressions to detect monotonic temporal trends in primary productivity (through the enhanced vegetation index, EVI) and climate (mean temperature and accumulated precipitation) at two spatial resolutions (10-km2 UTM squares and CORINE land-cover polygon level) over the period 2000–2020. We also determined how the strength of land-use and climate change affected the intensity of change in primary productivity at both spatial scales with multivariate linear regressions. We identified 339 hotspots (10-km2 UTM squares) and monotonic increments of temperature, EVI or both occurred in 43 %, 16 % and 22 % of them, respectively. Positive trends of the EVI were related to increasing temperatures and changes in shrubland and forest cover. Within the hotspots with monotonic increments in EVI and temperature, EVI increments occurred in 65 % of the CORINE polygons that did not change their land-cover type, with stronger increases in tree crops. Finally, the Natura 2000 network provides only moderate protection to reptile hotspots, being most of the vegetation types relatively underrepresented. The proportion of forest and shrubland protected by the Natura 2000 network was higher in hotspots where EVI changed. Our procedures are relevant to prioritize hotspots requiring ground monitoring that allows economic and time savings.

Biophilic elements in core sediments as records of coastal eutrophication in the Seto Inland Sea, Japan

This study presents vertical profiles of biophilic elements in core sediments from the Seto Inland Sea, Japan. We determined total organic carbon (TOC), total nitrogen (TN), total phosphorus (TP), biogenic silica (BSi), and phaeopigments in sediments from 80-cm-long cores collected from Hiuchi-Nada (Site A) and Harima-Nada (Site B). The vertical profiles are generally similar: all concentrations decrease downward from the top layer and show maximum values in the top layers for each parameter at both study areas. Among these biophilic elements, the correlation between BSi and TOC is particularly high, suggesting that diatoms are the main source of TOC in the sediments. The degradation rates at Site A in increasing order, as estimated by a steady-state diagenetic model (one-G model), are TOC ≈ BSi < TP < TN ≈ phaeopigments. However, these rates differ substantially from those at Site B, suggesting that the degradation rates might differ among sedimentation processes and environments. Using the one-G model and molecular composition (C:N) ratios, we estimate the origin (terrestrial and marine) for the amount of carbon before decomposition and followed its variation over the past approximately 200 years. We found that marine carbon is a major component and tends to be higher during the eutrophication period (1960–1990) at Site B, although not so much at Site A. At Site B the marine carbon content increases by about 25% during the eutrophication period, but at Site A no remarkable increase can be confirmed. These results are consistent with previous studies showing that the trend in primary production in the Seto Inland Sea since the eutrophication period has not been regionally homogeneous.

Mismatches between vegetation greening and primary productivity trends in South Asia – A satellite evidence

Vegetation greening contributes to gross carbon sequestration by plants and thus plays a vital role in mitigation of global warming. Terrestrial vegetation has a significant greening trend in South Asia (SA); however, it remains elusive how this greening translates to gross primary production (GPP) (proxy of gross carbon uptake by plants at ecosystem scale) in SA. In this study, we investigated the spatiotemporal dynamics of GPP in correspondence to leaf area increase (based on leaf area index as proxy of greening) over SA using remote sensing driven data on Google Earth Engine (GEE) cloud computation, during 2003–2017. We found a much weaker increase of GPP in SA as compared to the overall greening trend, primarily attributed to the disturbance in cropland activities of the region. Especially, greening was highly significant (p < 0.05) over the most irrigated and fertile Indo-Gangetic Plain (IGP) of SA, however GPP trend was non-significant (p > 0.05) over this region. Further, natural vegetation areas also showed low vegetation greening and GPP increase during the study period. The analysis of the potential drivers revealed that both climatic and anthropogenic stresses (intensive cropping, population pressure) had a negative impact on the regional GPP, especially in IGP. Our study indicated that the overwhelming greening of SA because of enhanced cropland activities, did not contribute much to GPP over the region. The restricted cropland canopy carbon uptake and low GPP increase in forests led to a lower than expected increase of gross carbon assimilation over SA in the context of climate changes and anthropogenic disturbances. Our study inferred that effective reforestation programs and conservation of natural vegetation areas are essential in SA for efficient vegetation carbon assimilation.

Reviews and syntheses: Trends in primary production in the Bay of Bengal – is it at a tipping point?

Abstract. Ocean primary production is the basis of the marine food web, sustaining life in the ocean via photosynthesis, and removing carbon dioxide from the atmosphere. Recently, a small but significant decrease in global marine primary production has been reported based on ocean color data, which was mostly ascribed to decreases in primary production in the northern Indian Ocean, particularly in the Bay of Bengal. Available reports on primary production from the Bay of Bengal (BoB) are limited, and due to their spatial and temporal variability difficult to interpret. Primary production in the BoB has historically been described to be driven by diatom and chlorophyte clades, while only more recent datasets also show an abundance of smaller cyanobacterial primary producers visually difficult to detect. The different character of the available datasets, i.e., direct counts, metagenomic and biogeochemical data, and satellite-based ocean color observations, make it difficult to derive a consistent pattern. However, making use of the most highly resolved dataset based on satellite imaging, a shift in community composition of primary producers is visible in the BoB over the last 2 decades. This shift is driven by a decrease in chlorophyte abundance and a coinciding increase in cyanobacterial abundance, despite stable concentrations of total chlorophyll. A similar but somewhat weaker trend is visible in the Arabian Sea, where satellite imaging points towards decreasing abundances of chlorophytes in the north and increasing abundances of cyanobacteria in the eastern parts. Statistical analysis indicated a correlation of this community change in the BoB to decreasing nitrate concentrations, which may provide an explanation for both the decrease in eukaryotic nitrate-dependent primary producers and the increase in small unicellular cyanobacteria related to Prochlorococcus, which have a comparably higher affinity to nitrate. Changes in community composition of primary producers and an overall decrease in system productivity would strongly impact oxygen concentrations of the BoB's low-oxygen intermediate waters. Assuming decreasing nitrate concentrations and concurrent decreasing biomass production, export, and respiration, oxygen concentrations within the oxygen minimum zone would not be expected to further decrease. This effect could be enhanced by stronger stratification as a result of future warming and thus possibly counteract oxygen decrease as a direct effect of stratification. Therefore, given a decrease in primary production, the BoB may not be at a tipping point for becoming anoxic, unless external nutrient inputs increase.

Quantifying vegetation response to environmental changes on the Galapagos Islands, Ecuador using the Normalized Difference Vegetation Index (NDVI)

The vegetation of the Galapagos Islands (Ecuador) is strongly influenced by climate. El Niño events, seasonality, isolation, volcanism, and increasing human activity define the ecosystems of the archipelago. Given their socio-cultural and economic importance, it is critical to monitor the response of Galapagos vegetation to changes in climate and assess its vulnerability. This study explores the potential to use Normalized Difference Vegetation Index (NDVI) as a proxy to describe trends in primary productivity in the Galapagos (2000–2019) and models the relationship between NDVI and climate variables including evaporation and atmospheric carbon dioxide concentration.From numerous possible co-variates compiled from reanalysis and satellites, we identify the independent variables that most strongly influence NDVI using the least absolute shrinkage and selection operator (LASSO) method. Significant variables, including carbon dioxide concentration, evaporation, and autocorrelation (1-month and 12-months lagged NDVI) are then used to model NDVI in a generalized linear model (GLM) framework. The model predicts NDVI more effectively where values for NDVI are high (high elevation, lush vegetation), and clearly reflects seasonality. Validation of the model across pixels produces R 2 values ranging from 0.05 to 0.94, and the mean R 2 is 0.57 (0.65 for elevation >20 m). This methodology has the potential to continuously and non-intrusively monitor vegetation changes in sensitive ecological regions, such as the Galapagos.

Long-term primary production trends in the Laurentian Great Lakes: a comparison of geochemical methods

Sediment cores from 12 locations throughout the Laurentian Great Lakes basin were analyzed for geochemical indicators of primary production. Sediment analytes included organic and inorganic contents, carbonates, sediment accumulation rates, total organic carbon and nitrogen concentrations, carbon and nitrogen isotope composition, and trends in spectroscopically inferred chlorophyll a (and its main diagenetic products). When multiple indicators were considered, production records related to recent cultural eutrophication and catchment activities were clear in the paleorecords. Indicators derived from loss-on-ignition (organic and inorganic content) were strongly associated with periods of human settlement in the catchments that increased overall sediment loads to the lakes. The ratio of carbon to nitrogen tracked catchment inputs of carbon, especially during periods of watershed development in western Lake Superior. Sediment records such as chlorophyll a and δ13Corg appear to be reliable indicators of trends in past algal abundance, particularly in Lake Erie, which has a well-known history of higher production and cultural eutrophication. These analytes also correlated well with past measured water quality surrogates for lake primary productivity and stressor data such as human populations in adjacent watersheds. A comparison among indicators revealed that several show redundancy as good proxies of production or productivity, though context was important. For instance, heavier isotopes of carbon and nitrogen are often prescribed as sedimentary indicators of lake productivity, but these two analytes were negatively correlated in Lake Superior, possibly due to long-term increases in cyanobacteria or changes in the nitrogen source. An increase in sediment carbonates can indicate summer blooms of cyanobacteria (a phenomenon that was clearly apparent in Lake Ontario) or catchment erosion. To make convincing geochemical inferences of primary production in the Great Lakes, it is recommended that a weight of evidence be built through the use of multiple indicators.

Recent trends in mountain lake primary production: evaluating the response to fish stocking relative to regional environmental stressors

Sia ME, Doyle RM, Moser KA. 2020. Recent trends in mountain lake primary production: evaluating the response to fish stocking relative to regional environmental stressors. Lake Reserv Manage. XX:XXX–XXX. Although mountain lakes are often remote, they are impacted by a myriad of stressors, including species introductions, atmospheric fertilization, and climate change. These stressors have the potential to increase primary production, which can threaten mountain lakes by decreasing water quality, reducing species richness, and lowering dissolved oxygen concentrations. The relative importance of these stressors as drivers of production is not well understood. We therefore investigated the importance of fish stocking, relative to other stressors, as a driver of primary production in mountain lakes. Our research focused on Uinta Mountain lakes, which, like many lakes in the western United States, were stocked with salmonid fish in the 1950s. In 2 stocked lakes and one unstocked lake, we reconstructed a record of ∼300 yr of primary production from lake sediments using changes in percentage of organic matter and spectrally inferred concentrations of chlorophyll a and its derivatives. With long-term trends in primary production, we determined that all 3 study lakes, including the unstocked lake, show unprecedented increases in primary production beginning in the 1950s. We attribute recent increases in primary production mainly to atmospheric deposition of nitrogen and climate warming, but do not rule out future impacts of fish stocking. Our article demonstrates how breakpoint analysis can be used to identify the most serious threats to mountain lakes, even if those lakes are impacted by multiple stressors or stressors originating from distant places.

Phytoplankton dynamics in a changing Arctic Ocean

Changes in the Arctic atmosphere, cryosphere and Ocean are drastically altering the dynamics of phytoplankton, the base of marine ecosystems. This Review addresses four major complementary questions of ongoing Arctic Ocean changes and associated impacts on phytoplankton productivity, phenology and assemblage composition. We highlight trends in primary production over the last two decades while considering how multiple environmental drivers shape Arctic biogeography. Further, we consider changes to Arctic phenology by borealization and hidden under-ice blooms, and how the diversity of phytoplankton assemblages might evolve in a novel Arctic ‘biogeochemical landscape’. It is critical to understand these aspects of changing Arctic phytoplankton dynamics as they exert pressure on marine Arctic ecosystems in addition to direct effects from rapid environmental changes.

Hidden Production: On the Importance of Pelagic Phytoplankton Blooms Beneath Arctic Sea Ice

AbstractRecent observations suggest that substantial phytoplankton blooms occur under sea ice on Arctic continental shelves during June and July. This is opposed to the traditional view that no significant biomass is produced in sea‐ice covered waters. However, no observational estimates are available on the Arctic‐wide primary production beneath sea ice. Here, using a fully coupled Arctic system model, we estimate that 63%/41% of the total primary production in the central Arctic occurs in waters covered by sea ice that is ≥50%/≥85% concentration. The total primary production there is increasing at a rate of 5.2% per decade during 1980–2018. Increased light transmission, due to the removal of sea ice, more extensive melt ponds, and thinner sea ice, is implicated as the main cause of increasing trends in primary production.

Spatial shifts in productivity of the coastal ocean over the past two decades induced by migration of the Pacific Anticyclone and Bakun's effect in the Humboldt Upwelling Ecosystem

Intensification and poleward expansion of upwelling favourable winds have been predicted as a response to anthropogenic global climate change and have recently been documented in most Eastern Boundary Upwelling Ecosystems of the world. To identify how these processes are impacting nearshore oceanographic habitats and, especially, long term trends of primary productivity in the Humboldt Upwelling Ecosystem (HUE), we analysed time series of sea level pressure, wind stress, sea surface and atmospheric surface temperatures, and Chlorophyll-a, as a proxy for primary productivity, along 26{\deg} - 36{\deg} S. We show that climate induced trends in primary productivity are highly heterogeneous across the region. On the one hand, the well documented poleward migration of the South Pacific Anticyclone (SPA) has led to decreased spring upwelling winds in the region between ca. 30{\deg} and 34{\deg} S, and to their intensification to the south. Decreased winds have produced slight increases in sea surface temperature and a pronounced and meridionally extensive decrease in surface Chlorophyll-a in this region of central Chile. To the north of 30{\deg} S, significant increases in upwelling winds, decreased SST, and enhanced Chlorophyll-a concentration are observed in the nearshore. We show that this increased in upwelling driven coastal productivity is probably produced by the increased land-sea pressure gradients (Bakun's effect) that have occurred over the past two decades north of 30{\deg} S. Thus, climate drivers along the HUE are inducing contrasting trends in oceanographic conditions and primary productivity, which can have far-reaching consequences for coastal pelagic and benthic ecosystems and lead to geographic displacements of the major fisheries.

Importance of nutrient loading and irrigation in gross primary productivity trends in India

Investigating the effects of various environmental factors on gross primary productivity (GPP) is crucial for quantifying the carbon exchange between the atmosphere and the terrestrial vegetation for managing climate change. Although it is well known that various natural and anthropogenic factors (e.g., climate change, agricultural activities, and atmospheric CO2 concentration change) can alter GPP, their relative influences are not clearly understood in every region. In this study, we consider several factors and investigate their roles in increasing the GPP in large parts of India. We considered about three decades (1980s to late 2000s) of GPP data and use a regression based systematic approach to find out the most likely cause explaining the trends in India. This study suggests that the common suspects like CO2 and climate may have limited influence on the GPP trends in India when compared to anthropogenic influences. Our results instead support the notion that GPP trends in India are mainly shaped by agricultural activities through nutrient loading (R2=0.68) and irrigation (R2=0.1). Overall, our study reveals the potential of agricultural activities in altering the carbon budget of a region.

Primary Production, an Index of Climate Change in the Ocean: Satellite-Based Estimates over Two Decades

Primary production by marine phytoplankton is one of the largest fluxes of carbon on our planet. In the past few decades, considerable progress has been made in estimating global primary production at high spatial and temporal scales by combining in situ measurements of primary production with remote-sensing observations of phytoplankton biomass. One of the major challenges in this approach lies in the assignment of the appropriate model parameters that define the photosynthetic response of phytoplankton to the light field. In the present study, a global database of in situ measurements of photosynthesis versus irradiance (P-I) parameters and a 20-year record of climate quality satellite observations were used to assess global primary production and its variability with seasons and locations as well as between years. In addition, the sensitivity of the computed primary production to potential changes in the photosynthetic response of phytoplankton cells under changing environmental conditions was investigated. Global annual primary production varied from 38.8 to 42.1 Gt C yr − 1 over the period of 1998–2018. Inter-annual changes in global primary production did not follow a linear trend, and regional differences in the magnitude and direction of change in primary production were observed. Trends in primary production followed directly from changes in chlorophyll-a and were related to changes in the physico-chemical conditions of the water column due to inter-annual and multidecadal climate oscillations. Moreover, the sensitivity analysis in which P-I parameters were adjusted by ±1 standard deviation showed the importance of accurately assigning photosynthetic parameters in global and regional calculations of primary production. The assimilation number of the P-I curve showed strong relationships with environmental variables such as temperature and had a practically one-to-one relationship with the magnitude of change in primary production. In the future, such empirical relationships could potentially be used for a more dynamic assignment of photosynthetic rates in the estimation of global primary production. Relationships between the initial slope of the P-I curve and environmental variables were more elusive.

Spatially heterogeneous trends in nearshore and offshore chlorophyll a concentrations in lakes Michigan and Huron (1998–2013)

Abstract Nutrient abatement programmes have been successfully implemented around the globe to reduce nutrient loading into aquatic ecosystems. Concurrently, the worldwide spread of invasive filter feeders, such as dreissenid mussels, may alter nutrient dynamics in invaded systems by sequestering nutrients away from pelagic zones and reducing primary production in offshore areas. Such is the case in the Laurentian Great Lakes of North America, where decades of nutrient abatement and the establishment of dreissenid mussels have seemingly resulted in more oligotrophic conditions and altered spatial patterns of nutrient availability and primary production. Recent studies have focused on whole lake trends in primary production despite spatial differences in tributary inputs, bathymetry, and other environmental conditions that can affect primary production in nearshore areas. Thus, we hypothesised that trends in nearshore chlorophyll concentrations in different areas may diverge in a manner consistent with spatial differences in nutrient input. To evaluate these differences in surface chlorophyll responses, we assessed temporal trends in four different areas of Lake Michigan and three different areas of Lake Huron. We hypothesised that in lakes Huron and Michigan, nearshore zones have experienced slower declines of chlorophyll concentrations relative to offshore zones. To assess this hypothesis, we estimated temporal trends of surface water chlorophyll concentrations (a proxy for primary production) from satellite imagery from 1998 to 2013. We calculated average surface chlorophyll concentrations for 10‐m depth intervals ranging from the shore (0–10 m) to offshore (&gt;90 m) during representative months of May, July, and September. We then analysed these data to determine if long‐term trends in surface chlorophyll varied by season, proximity to the shoreline, and water depth. The rates of annual change in chlorophyll concentrations in nearshore areas were markedly different to offshore trends in both lakes. Chlorophyll concentrations declined overtime in offshore areas, but nearshore chlorophyll concentrations were either stable (in May) or increased (in July and September) throughout the time series. Differences in chlorophyll concentrations among areas were prominent in Lake Michigan. While differences between the northern and southern basin have been previously documented, trends in chlorophyll concentrations also differed between the eastern and western sides of Lake Michigan. Despite similar bathymetry and geographic features to Lake Michigan, regional trends were not observed in Lake Huron. The results of this study are generally consistent with the nearshore shunt hypothesis, which predicts that dreissenid filtering, nutrient re‐suspension, and continued nutrient loading from tributaries can cause an increase in primary production in nearshore areas during periods of offshore oligotrophication. Thus, the localised effects of nutrient abatement programmes in a given lake will be influenced by complex interactions between lake bathymetry and the presence of non‐native filter feeding organisms.

Global ocean primary production trends in the modern ocean color satellite record (1998–2015)

Ocean primary production (PP), representing the uptake of inorganic carbon through photosynthesis, supports marine life and affects carbon exchange with the atmosphere. It is difficult to ascertain its magnitude, variability, and trends due to our inability to measure it directly at large scales. Yet it is paramount for understanding changes in marine health, fisheries, and the global carbon cycle. Using assimilation of ocean color satellite data into an ocean biogeochemical model, we estimate that global net ocean PP has experienced a small but significant decline −0.8 PgC y−1 (−2.1%) decade−1 (P < 0.05) in the 18-year satellite record from 1998 to 2015. This decline is associated with shallowing surface mixed layer depth (−2.4% decade−1) and decreasing nitrate concentrations (−3.2% decade−1). Relative contributions to PP by various types of ocean phytoplankton have changed, with decreases in production by intermediate-sized phytoplankton represented by chlorophytes (−14.3% decade−1). This is partially compensated by increases from the unique, more nutrient-efficient, coccolithophores (8.4% decade−1). Geographically, the North and Equatorial Indian Oceans are responsible for much of the decline in PP, falling 0.16 and 0.69 PgC y−1 decade−1, respectively. Reduced production by large, fast-growing diatoms along with chlorophytes characterizes the decline here. In contrast, increases in PP are found in the North and North Central Pacific. The increases here are led by chlorophytes in the North Pacific and the small cyanobacteria in the North Central Pacific. These results suggest that the multi-decadal satellite observational record, coupled with an underlying representation of marine biodiversity in a model, can monitor the uptake of carbon by phytoplankton and that changes, although small, are occurring in the global oceans.

High-Resolution Trophic Models Reveal Structure and Function of a Northeast Pacific Ecosystem

This paper examines the structure and dynamics of the marine ecosystem surrounding Haida Gwaii (an archipelago in the southeastern Gulf of Alaska). Based on previous research, a set of improved mass-balanced models was constructed in Ecopath with Ecosim (EwE) to represent ecosystem states existing circa 1900, 1950, and currently. These models feature increased taxonomic and ecological resolution relative to their predecessors across trophic levels and size classes from zooplankton to whales. A more detailed representation of Pacific herring (Clupea pallasii), including its age structure, predators, and prey, was introduced to permit modeling of the ecosystem role of herring as a forage fish, as well as the ecological impacts of herring fisheries. Gross ecosystem structure and herring trophodynamics were compared across ecosystem states using size spectra and ecological indicators, including mixed trophic impacts. The 1950 model was fitted to a comprehensive set of biomass and catch time series. Dynamic ecosystem simulations evaluated the influence of fishing, predation, other natural mortality, and primary productivity trends on ecosystem behavior since 1950, as well as the relative importance of top-down versus bottom-up forcing. Size spectra and ecosystem indicators suggest that the Haida Gwaii ecosystem has not undergone a radical structural shift since 1900, despite heavy exploitation of numerous marine mammals and fish. Moreover, mixed trophic impacts show that herring constitutes an important mid-trophic level node in the food web, participating in complex interactions with many predators, prey, and competitors. Dynamic ecosystem simulations demonstrate that trends in fishing mortality, trophic interactions, and primary productivity (correlated with the Pacific Decadal Oscillation) are all necessary to explain historical Haida Gwaii ecosystem behavior. These interacting drivers yield a mosaic of top-down and bottom-up trophic control for trophic interactions involving herring and throughout the food web. Simulation results also suggest that production of several herring, salmon, and groundfish stocks may have recently become partially decoupled from primary productivity, perhaps due to changes in copepod guild composition. These results also indicate that a biodiversity decline and “fishing down the food web” occurred off Haida Gwaii since 1950. Finally, the fitted 1950 model provides a robust platform for dynamic ecosystem simulations.

Abrupt shifts of productivity and sea ice regimes at the western Barents Sea slope from the Last Glacial Maximum to the Bølling-Allerød interstadial

Advanced knowledge of spatio-temporal constraints on the Barents Sea Ice Sheet during the late Weichselian glaciation overshadows relatively limited understanding of seasonal sea ice (experiencing an annual advance-retreat cycle) and primary productivity trends accompanying massive, abrupt climate changes during glacial-deglacial cycles. Such paleo-reconstructions are crucial prerequisites for improved comprehension and prediction of current and future climate change. Here, we investigate sea ice and phytoplankton biomarker distributions in a Barents Sea sediment core covering ca. 25.8–15.4 cal kyr BP to elucidate abrupt shifts of spring–summer sea ice concentrations and relative sympagic–pelagic productivity trends at the southwestern continental slope. Despite significant presence of seasonal sea ice, the Last Glacial Maximum (LGM) and initial shelf edge deglaciation (SEDG) at the core site are characterised by occurrence of productive coastal polynya adjacent to the maximum ice sheet extent. The onset of perennial (i.e. multi-year) ice cover and near-zero productivity during Heinrich Stadial 1 (HS1; ca. 18.0–16.3 cal kyr BP) accompanies significant meltwater fluxes from ice sheet debuttressing and the consequent stagnation of thermohaline circulation. Rapid sea ice retreat and unprecedented pelagic productivity observed after 16.3 cal kyr BP coincides with areal ice sheet deglaciation and is potentially linked to the release of sub-surface heat and nutrient reservoirs, together with reinvigorated deep water circulation following millennial heating of the deep ocean during HS1. We find that a multivariate fingerprinting approach involving assessment of both downcore and surface biomarker distributions is able to distinguish relative ice-algal and pelagic diatom productivity driven by sea ice dynamics.

Use of satellite images to characterize the spatio-temporal dynamics of primary productivity in hotspots of endemic Iberian butterflies

Abstract The Iberian Peninsula is one of the European regions with the highest number of endemic species. Therefore, it is imperative to identify species populations potentially affected by variations in ecosystem functioning. Since the emergence of data processed from satellites, the possibility of carrying out studies covering both a spatial and temporal dimension has increased, providing more comprehensive information about species population dynamics and ecosystems. Primary productivity is a crucial parameter for understanding ecosystem function and services because it is the basis of the trophic chain. This study examines the spatiotemporal variation in primary productivity over a 14-year temporal series (2000–2013) through the enhanced vegetation index (EVI). We focused on the hotspots of endemic diurnal butterflies in the Iberian Peninsula and obtained data on the primary productivity dynamics at these locations as indicators to optimize further conservation efforts. Within these hotspots, statistically significant yet spatially irregular trends were found at localized sites, mostly in mountain systems (the Cantabrian Mountains, Iberian System, Sierra de Guadarrama and Sierra Nevada). At 60% of these sites, primary productivity significantly decreased. Two endemic species, the Sierra Nevada blue (Polyommatus golgus) and the Puerto del Lobo butterfly (Agriades zullichi), which are classified by the International Union for Nature Conservation (IUCN) as “Vulnerable” and “Endangered”, respectively, are present in localities where primary productivity showed a marked decline despite being within the Natura 2000 Network. The procedures developed here, which are based on consistent temporal trends of primary productivity, can serve as a tool to detect among biodiversity hotspots those locations where environmental change is unequivocal and hence further monitoring is needed.

Long-term changes in the primary productivity of migratory caribou (Rangifer tarandus) calving grounds and summer pasture on the Quebec-Labrador Peninsula (Northeastern Canada): the mixed influences of climate change and caribou herbivory

At high herbivore density, herbivory can reduce forage abundance, potentially contributing to habitat degradation and driving changes in herbivore population size or range use, in accordance with the exploitation ecosystem hypothesis. The migratory Riviere-George caribou herd (RGH, Rangifer tarandus) of the Quebec-Labrador Peninsula (Canada) has experienced a large decline in population size since the population peaked in the early 1990s, with similarly large changes in seasonal range use. Demographic changes are suspected to have influenced forage abundance and caribou range use through density-dependent interactions between caribou and their habitat. We used the Normalized Difference Vegetation Index (NDVI) to examine relationships between RGH caribou density and range productivity from 1991 to 2011. A modelling approach was used to control for the response of climate and to isolate the influence of caribou herbivory on primary productivity. Significant negative relationships were identified between caribou density and primary productivity, after controlling for climatic variation, for the global RGH calving grounds (r2 = 0.54–0.55) and summer range (r2 = 0.42–0.51), but not for the “core” ranges, where caribou density was highest. Positive temporal trends in primary productivity appeared to reflect the decline in RGH population size, suggesting vegetation recovery following reductions in caribou abundance. Climate warming (of up to + 1.5 °C per decade) was most responsible for the strong positive trends in primary productivity observed over the 1991–2011 period, but decreases in RGH herbivory likely also contributed to the increases in range productivity. Forage access likely improved over the study period, which may have influenced RGH range use and habitat selection.

Seasonal diet composition of Pyrenean chamois is mainly shaped by primary production waves.

In alpine habitats, the seasonally marked climatic conditions generate seasonal and spatial differences in forage availability for herbivores. Vegetation availability and quality during the growing season are known to drive life history traits of mountain ungulates. However, little effort has been made to understand the association between plant phenology and changes in the foraging strategies of these mountain dwellers. Furthermore, this link can be affected by the seasonal presence of livestock in the same meadows. The objective of this work was to study the seasonal changes in diet composition of Pyrenean chamois (Rupicapra p. pyrenaica) and its relationship to primary production trends in a Mediterranean alpine environment. Moreover, diet composition in two populations with contrasting livestock pressure was compared in order to study the effect of sheep flocks on the feeding behaviour of chamois. From 2009 to 2012, monthly diet composition was estimated by cuticle microhistological analysis of chamois faeces collected in the eastern Pyrenees. The primary production cycle was assessed by remote sensing, using the Normalized Difference Vegetation Index. Additionally, the diet of sheep sharing seasonally the subalpine and alpine meadows with chamois was analysed. Diet selection of chamois and sheep and their overlap was also assessed. Our results show an intra-annual variation in the diet composition of Pyrenean chamois and demonstrate a strong relationship between plant consumption dynamics and phenology in alpine areas. In addition, Calluna vulgaris, Cytisus spp. and Festuca spp., as well as forbs in the summer, are found to be key forage species for Pyrenean chamois. Furthermore, this study couldn’t detect differences between both chamois populations despite the presence of sheep flocks in only one area. However, the detection of a shift in the diet of chamois in both areas after the arrival of high densities of multi-specific livestock suggest a general livestock effect. In conclusion, Pyrenean chamois are well adapted to the variations in the seasonal availability of plants in alpine habitats but could be disturbed by the seasonal presence of livestock. Due to the key plants in their diet, we suggest that population management programmes should focus on the preservation of mixed grasslands composed of patches of shrubs and herbs. The effects of climate change and shrub expansion should be studied as they may potentially affect chamois population dynamics through changes in habitat composition and temporal shifts in forage availability.

Biogeochemical responses to climate change and anthropogenic nitrogen deposition from a ∼200-year record from Tianchi Lake, Chinese Loess Plateau

Human activities over the last ∼100 years have fundamentally changed the biogeochemistry of the global nitrogen cycle. For example, increased nitrogen deposition from industrial and agricultural sources has been linked to lake acidification and nutrient fertilization, and thus it has the potential to significantly influence lake ecosystems. Records of anthropogenic nitrogen deposition from alpine lakes are sparse in China, which limits our understanding of its effects on remote alpine lake ecosystems. In this study, we analyzed multiple geochemical proxies at Tianchi Lake (2430 m a.s.l.), which is part of the Liupan Mountains National Nature Reserve in the central Chinese Loess Plateau (CLP). We measured total nitrogen (TN) concentrations, C/N ratios and nitrogen stable isotope ratios (δ15N), as well as a biological proxy (spectrally-inferred chlorophyll a), from a well-dated sediment core spanning the past ∼200 years. Our aim was to examine anthropogenic nitrogen deposition to the lake and to assess its implications for lake primary production. We found that δ15N was stable prior to ∼1980, but it decreased significantly thereafter. This is consistent with documented changes in anthropogenic nitrogen deposition over the past ∼200 years, and it indicates that the δ15N record of Tianchi Lake likely reflects anthropogenic nitrogen deposition, at least in this region. Prior to ∼1980, the trend in primary production of Tianchi Lake agrees with the trend of reconstructed regional temperature, when reactive nitrogen emissions in China were very low. This suggests that temperature was likely the main factor driving lake primary production before ∼1980. Primary production has increased significantly since ∼1980, consistent with the continued rising temperature and with enhanced nitrogen deposition, indicating that both factors are simultaneous drivers. Although the current data for Tianchi Lake are insufficient to unequivocally determine which of the two stressors is more important after the 1980s, temperature likely played the more significant role in driving primary production. This is because the lake is phosphorus-limited today, and in addition there is a strong association between temperature and chlorophyll a over the past ∼200 years. Continuing global warming and increasing nitrogen deposition in the future will likely further affect the fragile alpine ecosystems in the region.