The elemental stoichiometry of carbon (C), nitrogen (N) and phosphorus (P) regulates marine biogeochemical cycles and underpins the Redfield ratio paradigm. However, its global variability and response to environmental change remain poorly constrained. Here we compile a global dataset of 56,031 plankton (particulate) and 388,515 seawater (dissolved) samples from 1971 to 2020, spanning surface to 1,000 m depth, to assess spatial and temporal dynamics in marine C:N:P ratios. We show that planktonic C:P and N:P, and oceanic C:N and C:P ratios, consistently exceed Redfield ratio throughout the study period, indicating widespread deviation from canonical stoichiometry. Planktonic C:N and N:P ratios rose markedly in the late twentieth century, followed by a decline, suggesting a progressive alleviation of P limitation, probably driven by increased anthropogenic P inputs. Depth-resolved patterns show decreasing oceanic C:N and C:P, and increasing N:P ratios with depth, attributable to differential remineralization and microbial nutrient cycling. Our findings highlight dynamic, non-static stoichiometric patterns over decadal scales, offering critical observational constraints for refining the representation of elemental cycling in biogeochemical models and improving projections of marine ecosystem responses to global change. Fifty years of plankton and water samples show that the proportion of carbon, nitrogen and phosphorus in the ocean now substantially differs from the Redfield ratio, probably reflecting a reduction in phosphorus limitation.

The Indian River Lagoon (IRL) on Florida’s east-central coast is a highly eutrophic, urbanized estuary where, beginning in 2011, multiple harmful phytoplankton blooms were followed by catastrophic seagrass losses. Since then, in many locations where seagrass was lost, the rhizophytic green macroalga Caulerpa prolifera has become the dominant benthic cover. Although the habitat value of C. prolifera compared to the seagrass Halodule wrightii was assessed in the IRL during the late 1980s, there is no information regarding its current habitat value following the catastrophic losses of seagrass. Therefore, the habitat function of C. prolifera in the IRL was assessed during a period of very low seagrass cover by quantitively sampling epifauna inhabiting this macroalga. The benthic habitat cover and faunal composition of four C. prolifera sites in the IRL were determined between 2020–2021. Benthic cover varied by site and event with variable

Lake Okeechobee is a shallow subtropical lake that is critically important for south Florida agriculture and the Everglades. In summer, the lake typically experiences strong blooms of cyanobacteria including toxin producing Microcystis aeruginosa. To understand the dynamics of these blooms and water quality in the lake, a coupled hydrodynamic-biogeochemical model based on the Regional Ocean Modeling System (ROMS) has been developed. The biogeochemical model was constructed to simulate major biogeochemical processes including nitrogen (N) and phosphorus (P) cycles, phytoplankton growth, zooplankton grazing, and microbial loop, among others. A three-year (2018-2020) simulation was carried out and calibrated with available in situ and remote sensing data for key physical and biogeochemical parameters. Although model and data generally agree in spatial patterns and seasonal cycles, significant discrepancies exist including exact timings of the blooms and dissolved inorganic and organic P concentrations. Model results indicate that Lake Okeechobee typically exhibits a two-layer circulation in summer with surface and bottom currents generally moving in the opposite directions. This feature couples with diurnal cycles of atmospheric forcing (winds and heating/cooling) and diel vertical migration (DVM) of Microcystis to strongly affect not only the spatial patterns of cyanobacteria blooms but also the bloom intensity in summertime. Horizontally, both model results and remote sensing images indicate that cyanobacteria distributions are concentrated in the central and northern lake during summer and in western lake in spring and fall, in responses to the prevailing winds. Consistent with previous laboratory and observational studies, model results also suggest that, among the two main nutrients N and P, nitrogen is likely the primary limiting nutrient for phytoplankton growth along the northwestern coast where dissolved inorganic nitrogen is typically depleted in summer. In the central and southeastern lake, nutrient concentrations are relatively higher, and light and winds are likely the main factors limiting phytoplankton blooms. In addition, surface winds and water temperature are important in regulating the seasonality of phytoplankton blooms. The model, however, is limited by the uncertainties of key biogeochemical parameters including the specifics of Microcystis vertical migration, and sediment-water interactions including nutrient fluxes and sediment transport. Nevertheless, with further development, this model can be useful for forecasting water quality and phytoplankton blooms and to assist in water management decision-making in the future.

This review examines the changing distribution of pelagic Sargassum in the North Atlantic over the past four decades and how boundary current circulation enhances nutrient supply, productivity, and growth. Early explorers first described Sargassum in the Sargasso Sea and recognized the physical connectivity of "Gulfweed" to neritic populations in the Gulf of Mexico/America. In the 1980s, studies showed that Sargassum is more productive in neritic waters where it has lower carbon to nitrogen (C:N) and C to phosphorus (C:P) ratios. Sargassum productivity and growth are limited by both N and P, although P is often the primary limiting nutrient. The origin of the Great Atlantic Sargassum Belt (GASB) in 2011 was north the Amazon River mouth, suggesting this riverine nutrient source contributed to its development. This is supported by Sargassum tissue analysis and biomass increases/decreases between extreme flood/drought years in the Amazon basin. Comparison of the nutrient composition of Sargassum tissue (n= 849) from the 1980s with post-2010 and post-2020 showed increased %C (28 %), %N (55 % overall; 95 % in the Sargasso Sea), and N:P (50 %) but decreased %P (6 %) over the past four decades. Measurement of stable N isotopes (δ15N) in Sargassum revealed enriched δ15N correlated with increasing %N, pointing to the importance of terrestrial runoff, wastewater discharges, and coastal upwelling as potential N sources. We additionally report enriched levels of N and P in the western tropical region of the GASB, illustrating the importance of recent nutrient enrichment, especially P, to the excessive Sargassum biomass in the GASB.

Coral reefs are facing a constant barrage of human impacts, including eutrophication, overharvesting and climate change. While the local effects of overharvesting have been well-studied, regional nutrient loading from anthropogenic activities on land and global climate change-induced disturbances are increasing in magnitude and necessitating cross-scale multi-stressor approaches for coral reef ecology. Here, we expand on longstanding theory to develop an integrated multi-stressor framework for coral reefs. We show that: (i) The geometry of a simple, empirically motivated model suggests nutrients and harvesting can operate similarly, and synergistically, in driving shifts from coral- to algae-dominated reefs, resulting in clear context-dependent management implications; and (ii) this same geometry suggests climate-driven coral mortality can drive the presence of long transients and climate-driven alternate states, even in moderately impacted ecosystems. Reefs seemingly in a “safe space” based on individual stressors may in fact be much more susceptible to increasingly frequent storms and bleaching events in multi-stressor conditions. By integrating these findings with general ecological and theoretical concepts, we suggest that responses in benthic composition may act as “signatures of change” to multi-stressors, allowing us to develop a predictive and generalizable multi-stressor framework for coral reefs under global change. In line with this theory, we detail empirical evidence from Barbados of historical changes in reef composition and multi-stressor impacts within our framework. By bridging coral reef ecology and general ecological concepts, we can better understand ecosystem functioning and resilience in these important yet highly threatened systems.

Symbioses between primary producers and bacteria are crucial for nutrient exchange that fosters host growth and niche adaptation. Yet, how viruses that infect bacteria (phages) influence these bacteria-eukaryote interactions is still largely unknown. Here, we investigate the role of viruses on the genomic diversity and functional adaptations of bacteria associated with pelagic sargassum. This brown alga has dramatically increased its distribution range in the Atlantic in the past decade and is predicted to continue expanding, imposing severe impacts on coastal ecosystems, economies, and human health. We reconstructed 73 bacterial and 3963 viral metagenome-assembled genomes (bMAGs and vMAGs, respectively) from coastal Sargassum natans VIII and surrounding seawater. S. natans VIII bMAGs were enriched in prophages compared to seawater (28

Water from the Lake Okeechobee watershed historically flowed south through the Everglades. Hydrologic alterations created the Lake Okeechobee Waterway, where lake water is periodically shunted east to the St. Lucie Estuary (C-44 canal) and west to the Caloosahatchee River and Estuary (C-43 canal). Within the last two decades, Microcystis blooms have developed in Lake Okeechobee and been discharged to the downstream urbanized estuaries, resulting in negative environmental and human health impacts. To better understand drivers of cyanobacterial blooms across this modified waterway, two cruises were conducted from the St. Lucie Estuary through Lake Okeechobee to the Caloosahatchee River Estuary during 2019 and 2020. Opportunistic sampling was also conducted during Microcystsis blooms. Cruise stations were sampled for environmental parameters, dissolved nutrients, chlorophyll a, cyanobacterial cell concentrations, and microcystins, as well as particulate organic matter (POM) nutrient properties. Higher ammonium (NH4+), nitrate + nitrite (NO3-), dissolved inorganic nitrogen (DIN), soluble reactive phosphorus (SRP), total dissolved phosphorus (TDP), and POM stable N isotope (delta N-15) values were observed in the estuaries and Kissimmee River than in Lake Okeechobee. The nitrogen to phosphorus ratio (N:P), microcystins, and Microcystis cell concentrations were higher in Lake Okeechobee than documented over past decades. During Microcystis blooms, high NH4+, SRP, total dissolved nitrogen (TDN), TDP, and sucralose were observed with elevated algal delta N-15. These results demonstrate the importance of local basin contributions, including those within the lake, to estuarine Microcystis blooms. This suggests that decreasing nutrient loading within the St. Lucie and Caloosahatchee estuaries would help to mitigate these urban blooms. High POM delta N-15 values, NO3- concentrations, and N:P ratios in the Kissimmee River suggest that expanding urbanization north of the lake represents an increasing human N source contributing to cyanobacterial blooms in Lake Okeechobee.

The coastal communities of Lee County, Florida, USA have grown rapidly since the 1970s. In this county, drainage ditches, canals, creeks, and the Caloosahatchee River Estuary often have high concentrations of nutrients and bacteria limiting their designated uses. Septic systems have previously been identified as a major pollution source in some areas of Lee County; therefore, this study sought to identify the extent of this issue throughout the county. To accomplish this, surface water samples were collected at 25 ditch, creek, or canal sites suspected of human waste contamination from septic systems in various drainage basins throughout Lee County during January 2020-January 2021. Water samples were analyzed for nutrients, dual stable nitrate isotopes (δ15N-NO3-, δ18O-NO3-), fecal indicator bacteria (enterococci, Escherichia coli), a molecular tracer of human waste (HF183), and chemical tracers of human waste (the artificial sweetener sucralose, pharmaceuticals). Particulate organic matter (POM) and macrophytes were also collected and analyzed for stable carbon (δ13C) and nitrogen (δ15N) isotopes, as well as elemental composition (C:N:P). To broaden the assessment of stable isotope values and C:N:P, archived macrophyte samples from 2019 were also included in analyses. Ammonium concentrations were high (> 4.3 μM) in 55 % of samples. Fecal bacteria were high in 66 % of samples. HF183 was detected in 50 % of samples and positively correlated with enterococci (r = 0.32). Sucralose concentrations were high (> 380 ng/L) in 54 % of samples, while carbamazepine was detected in 40 % of samples. Human waste N sources were indicated by δ15N > 3.00 ‰ at 44 % of sites by δ15N-NO3-, 68 % of sites by POM, and at 100 % of sites where macrophyte samples were collected. This large-scale study provides evidence of widespread human waste pollution throughout Lee County and can help guide infrastructure improvements to promote sustainable development. These findings should be applicable to urbanized regions globally that are experiencing declines in water quality and harmful algal blooms due to development with inadequate infrastructure.

In Florida's Indian River Lagoon (IRL), anthropogenic eutrophication has resulted in harmful algal blooms and catastrophic seagrass losses. Hoping to improve water quality, policy makers enacted fertilizer bans, assuming that this would reduce the nitrogen (N) load. To assess the effectiveness of these bans, seawater and macroalgal samples were collected at 20 sites “pre” and ~ five-years “post” bans and analyzed to determine concentrations of dissolved nutrients and stable nitrogen isotope values (δ15N). Higher concentrations of ammonium and nitrate were observed post-ban and macroalgal δ15N values increased. A comparison of nutrient concentrations and δ15N between brown tide (Aureoumbra lagunensis) blooms indicated that the post-ban bloom was more strongly N-enriched with higher δ15N values than the pre-ban bloom, which had depleted values in the range of fertilizers. These data indicate a primary role of human waste influence in the IRL, suggesting that current management actions have been insufficient at mitigating eutrophication.

The Indian River Lagoon (IRL) on Florida’s east-central coast is a highly developed eutrophic estuary, experiencing harmful algal blooms (HABs). Beginning in 2011, the IRL experienced multiple phytoplankton HABs that were followed by widespread seagrass losses and expanding blooms of the rhizophytic macroalga Caulerpa prolifera. To better understand factors related to the changing benthic cover, long-term monitoring data spanning 2011–2020 for seagrass and C. prolifera percent cover at six locations in the northern IRL and Banana River Lagoon were considered in multivariate analyses with environmental parameters (temperature, salinity, pH, dissolved oxygen, etc.), dissolved nutrient and chlorophyll-a concentrations, and macroalgal carbon (δ13C) and nitrogen (δ15N) stable isotopes, elemental composition (%C, %N, %P), and nutrient ratios (C:N:P). Data reduction using the global Bio-Env + STepwise (BEST) procedure followed by linkage tree (LINKTREE) analyses indicated the variable most correlated to annual differences in benthic cover was macroalgal C:P. Following seagrass losses, P availability increased, as the result of heavy rainfall, increased sediment flux, and/or more bioavailable P due to seagrass losses. The most correlated variables among differences in location were C:P, δ13C, and salinity, which could be related to less urbanization at the northernmost sites that had lower percent cover of C. prolifera. While not identified as a significant variable, the increase in C. prolifera was associated with four years (2016–2019) of high ammonium concentrations (6.26 µM) and macroalgal δ15N values (+8.67 ‰), linking the blooms to the influence of human waste. The variables identified in this work as related to benthic cover suggest that reducing stormwater runoff and inputs of human waste will promote the recovery of seagrasses in the IRL. These findings have implications for urbanized estuaries experiencing seagrass loss globally.

Tropical macroalgae serve importance ecological roles on coral reefs but can supplant corals in phase shifts as shown worldwide. Thus, it is important to understand their fundamental photophysiology and effects on calcification mechanisms. We examined organic δ13C, inorganic CaCO3 δ13C and δ18O, and organic

Nitrogen (N) loading can affect estuarine food webs through alteration of primary producers. In the Indian River Lagoon (IRL), Florida there has been long-term N enrichment, worsening phytoplankton blooms, large-scale macroalgal blooms, and catastrophic seagrass losses. To investigate how N enrichment affects higher trophic levels and food webs in the IRL, nutrient availability was compared to primary producer and faunal stable N (δ15N) isotope values. Seawater samples were collected in the IRL for dissolved nutrient, chlorophyll-a, and particulate organic matter δ15N analyses. Macrophytes and fauna were also collected for δ15N analyses. Throughout the IRL, N was elevated but was highest in the northern IRL and Banana River Lagoon. δ15N was enriched in these segments for most samples to levels characteristic of human-waste impacted estuaries. Variability in δ15N among lagoon segments suggests a low level of trophic connectivity. Decreasing N loading to the IRL and other eutrophic estuaries may help improve resiliency.

Wastewater management is a critical issue globally. In Florida, the importance of this issue is heightened by the proximity to sensitive ecosystems. Distributed wastewater treatment units (DWTU) are a recent, state-approved alternative to septic system conversions to centralized sewer infrastructure. In this study, the performance of a DWTU was tested at a new residence in Lake Hamilton, FL. A monitoring well was installed downgradient of the DWTU absorption field to establish baseline groundwater conditions prior to occupation of the residence. The residence was occupied, after which groundwater, DWTU influent, and effluent samples were collected. Many effluent parameters significantly decreased compared to influent, including ammonia (NH3; 97%), total Kjeldahl nitrogen (TKN; 95%), total nitrogen (TN; 88%), the TN:TP ratio (84%), fecal coliforms (92%), carbonaceous biochemical oxygen demand (CBOD; 96%), and total suspended solids (TSS; 96%). In the groundwater, nutrient concentrations initially increased compared to the baseline data, but eventually decreased, demonstrating that the DWTU was effective at improving quality of wastewater effluent. These systems could be especially effective in sensitive areas where advanced wastewater treatment has been mandated or is needed.

Blooms of various types of seaweeds have been reported worldwide, with recent expansions in surface waters. While most of the expansions have been attributed to eutrophication due mainly to human activities, any potential role of climate change is unclear. Here we show that, in the East China Sea and Yellow Sea, increased biomass of Sargassum horneri ( S. horneri, brown seaweed) from 2000 to 2021 appears to be caused primarily by ocean warming, as S. horneri prefers a certain temperature range to grow. In contrast, while increases of Ulva prolifera ( U. prolifera, green seaweed) in the same regions might also be related to ocean warming, during the same period, human activities such as coastal aquaculture or seaweed mitigation may muddle such effects. With the projected ocean warming in the next decades, we hypothesize that S. horneri blooms may occur earlier during the year and may continue to expand in the future.

As human population growth has expanded in Southwest Florida, water quality has become degraded with an increased occurrence of harmful algal blooms (HABs). Red tide (Karenia brevis) originating offshore, intensifies in nearshore waters along Florida's Gulf Coast, and blue-green algae (Microcystis spp.) originating in Lake Okeechobee is discharged into the Caloosahatchee River. These HABs could be enhanced by anthropogenic nitrogen (N) and phosphorus (P) from adjacent watersheds. North Fort Myers is a heavily developed, low-lying city on the Caloosahatchee River Estuary serviced by septic systems with documented nutrient and bacterial pollution. To identify sources of pollution within North Fort Myers and determine connections with downstream HABs, this multiyear (2017-2020) study examined septic system- groundwater- surface water couplings through the analysis of water table depth, nutrients (N, P), fecal indicator bacteria (FIB), molecular markers (HF183, GFD, Gull2), chemical tracers (sucralose, pharmaceuticals, herbicides, pesticides), stable isotopes of groundwater (δ15N-NH4, δ15N-NO3) and particulate organic matter (POM; δ15N, δ13C), and POM elemental composition (C:N:P). POM samples were also collected during K. brevis and Microcystis spp. HAB events. Most (>80%) water table depth measurements were too shallow to support septic system functioning (<1.07 m). High concentrations of NH4+ and NOx, up to 1094 μM and 482 μM respectively, were found in groundwater and surface water. δ15N values of groundwater (+4.7‰) were similar to septic effluent (+4.9‰), POM (+4.7‰), and downstream HABs (+4.8 to 6.9‰), indicating a human waste N source. In surface water, FIB were elevated and HF183 was detected, while in groundwater and surface water sucralose, carbamazepine, primidone, and acetaminophen were detected. These data suggest that groundwater and surface water in North Fort Myers are coupled and contaminated by septic system effluent, which is negatively affecting water quality and contributing to the maintenance and intensification of downstream HABs.

Macroalgal blooms are increasing on the Belize Barrier Reef (BBR) as scleractinian coral cover declines. Although some have attributed this to reduced grazing, the role of land-based nutrient pollution has not been assessed. Nutrient enrichment was quantified through macroalgal tissue analysis from Belize City to the offshore fore reef and at several central BBR lagoon sites. These recent data were compared to baseline data from the 1980s. Significant nearshore-to-offshore gradients of %N, %P and δ13C in macroalgae all indicated land-based sources of these nutrients. Macroalgal δ15N values were generally enriched in nearshore waters where values matched those reported for human sewage. Notably, the N:P ratios of recent macroalgae measurements were elevated at all sites, more than two-fold higher than values from the 1980s (~30: 1 to 70:1). These results support the hypothesis that nitrogen enrichment from land-based sources has increased phosphorus limitation driving macroalgal blooms and coral stress on the BBR.

The extensive blooms of the pelagic Sargassum in the Atlantic raised the question of whether this brown seaweed may play an important role in climate change mitigation through carbon fixation and carbon sequestration, as argued in several recent papers. Using simple calculations and published values on Sargassum coverage, biomass density, carbon/biomass ratio, primary productivity, and carbon sequestration efficiency, we show that the total carbon stock in pelagic Sargassum of the entire Atlantic, even during the peak month, is unlikely to exceed 3.61 x 10(-3) Pg C, and carbon fixation cannot exceed 6.0 million tons C month(-1). While the carbon fixation estimate represents an upper bound, it is still <0.2% of carbon fixation by phytoplankton in the Atlantic Ocean. The carbon stock estimate is 2000 times lower than predicted using a machine learning model in another recent paper. In contrast, carbon sequestration by Sargassum appears significant locally within the Atlantic Sargassum belt. The analysis further suggests that, while the Atlantic pelagic Sargassum may play an important role in affecting local carbon budget and carbon sequestration, its contribution to either carbon stock or carbon sequestration at a global scale may be insignificant. This, however, does not diminish the importance of Atlantic pelagic Sargassum in many other aspects. (C) 2021 Elsevier B.V. All rights reserved.

The pelagic brown macroalgae Sargassum spp. have grown for centuries in oligotrophic waters of the North Atlantic Ocean supported by natural nutrient sources, such as excretions from associated fishes and invertebrates, upwelling, and N2 fixation. Using a unique historical baseline, we show that since the 1980s the tissue %N of Sargassum spp. has increased by 35%, while %P has decreased by 44%, resulting in a 111% increase in the N:P ratio (13:1 to 28:1) and increased P limitation. The highest %N and δ15N values occurred in coastal waters influenced by N-rich terrestrial runoff, while lower C:N and C:P ratios occurred in winter and spring during peak river discharges. These findings suggest that increased N availability is supporting blooms of Sargassum and turning a critical nursery habitat into harmful algal blooms with catastrophic impacts on coastal ecosystems, economies, and human health.

Harmful algal blooms that can produce toxins are common in the Indian River Lagoon (IRL), which covers -250 km of Florida's east coast. The current study assessed the dynamics of microcystins and saxitoxin in six segments of the IRL: Banana River Lagoon (BRL), Mosquito Lagoon (ML), Northern IRL (NIRL), Central IRL (CIRL), Southern IRL (SIRL), and the St. Lucie Estuary (SLE). Surface water samples (n = 40) collected during the 2018 wet and 2019 dry season were analyzed to determine associations between toxins and temperature, salinity, pH, oxygen saturation, concentrations of dissolved nutrients and chlorophyll-a, presence of biosynthetic genes for toxins, relative abundance of planktonic species, and composition of the microbial community. The potential toxicity of samples was assessed using multiple mammalian cell lines. Enzyme-Linked Immunosorbent Assays were used to determine concentrations of microcystins and saxitoxin. Overall, the microcystins concentration ranged between 0.01-85.70 mu g/L, and saxitoxin concentrations ranged between 0.01-2.43 mu g/L across the IRL. Microcystins concentrations were 65% below the limit of quantification (0.05 mu g/L), and saxitoxin concentrations were 85% below the limit of detection (0.02 mu g/L). Microcystins concentrations were higher in the SLE, while saxitoxin was elevated in the NIRL and BRL. Cytotoxicity related to the presence of microcystins was seen in the SLE during the wet season. No significant patterns between cytotoxicity and saxitoxin were identified. Dissolved nutrients were identified as the most highly related parameters, explaining 53% of microcystin and 47% of saxitoxin variability. Multivariate models suggested cyanobacteria, flagellates, ciliates, and diatoms as the subset of microorganisms whose abundances were maximally correlated with saxitoxin and microcystins concentrations. Lastly, biosynthetic genes for microcystins were detected in the SLE and for saxitoxin in the BRL and NIRL. These results highlight the synergistic roles environmental and biological parameters play in influencing the dynamics of toxin production by harmful algae in the IRL.

Almost 50 years ago, Michael Rosenzweig pointed out that nutrient addition can destabilise food webs, leading to loss of species and reduced ecosystem function through the paradox of enrichment. Around the same time, David Tilman demonstrated that increased nutrient loading would also be expected to cause competitive exclusion leading to deleterious changes in food web diversity. While both concepts have greatly illuminated general diversity-stability theory, we currently lack a coherent framework to predict how nutrients influence food web stability across a landscape. This is a vitally important gap in our understanding, given mounting evidence of serious ecological disruption arising from anthropogenic displacement of resources and organisms. Here, we combine contemporary theory on food webs and meta-ecosystems to show that nutrient additions are indeed expected to drive loss in stability and function in human-impacted regions. Our models suggest that destabilisation is more likely to be caused by the complete loss of an equilibrium due to edible plant species being competitively excluded. In highly modified landscapes, spatial nutrient transport theory suggests that such instabilities can be amplified over vast distances from the sites of nutrient addition. Consistent with this theoretical synthesis, the empirical frequency of these distant propagating ecosystem imbalances appears to be growing. This synthesis of theory and empirical data suggests that human modification of the Earth is strongly connecting distantly separated ecosystems, causing rapid, expansive and costly nutrient-driven instabilities over vast areas of the planet. Similar to existing food web theory, the corollary to this spatial nutrient theory is that slowing down spatial nutrient pathways can be a potent means of stabilising degraded ecosystems.