An Ecosystem Approach for The Sustainable Use and Management of the Lake Victoria Ecosystem

The key to achieving sustainable development is striking a balance between the exploitation of natural resources for socioeconomic development and the preservation of ecosystem services, which are essential to everyone's well-being and livelihood. This can be achieved by using the ecosystem approach which promotes fair conservation and sustainable use of both land, water and living resources. Over the years, human activities have played an important role in the degradation of natural ecosystems, either due to pollution or unsustainable development. Lake Victoria is the best example of the impact of anthropogenic activity on ecosystems, as it has undergone dramatic biophysical and geochemical changes in a relatively short time. Managing Lake Victoria requires the coordinated efforts of individuals, landowners, research institutions, community groups, and the government. This lake is an important group of natural resources due to its ecosystem services and often unique cultural characteristics hence need for sustainable management. This article focuses on using the ecosystem method to determine optimal management approaches for the Lake Victoria ecosystem's long-term sustainability. The article proposes an integrated stakeholder-based management system and holistic regional development in lake areas that will preserve natural ecosystems without compromising the sustainable use of ecosystem services. As a result, there is a need to remedy the lake ecosystem's degradation in order to retain the shared ecological services that support socioeconomic well-being

Ecological modeling of Lake Victoria

Lake Victoria is of immense ecological and socio-economic significance for the riparian communities. However, the lake is faced with human induced pressures such as overfishing, introduction of alien species, increased eutrophication and climate change impacts. Its large spatial extent and complex ecology have also limited the understanding of the system dynamics, major processes, drivers and responses. To address this challenge, Atlantis, the first end-to-end whole ecosystem model for the lake was developed. First, a Regional Oceanographic Model System (ROMS) for the lake was developed to provide hydrodynamic forcing data for the ecosystem model. The ROMS model was based on real bathymetry, river runoff and atmospheric forcing data. Results from this model revealed diverse spatial and temporal water circulation patterns and temperature trends in Lake Victoria. The ROMS output provided water currents and temperature forcing data for the Atlantis model. The Lake Victoria Atlantis model was spatially resolved into 12 unique dynamic areas based mainly on their biophysical attributes. A total of 38 functional groups constituted the biological model while fishing was implemented by four fleets with different targeting options. The model was validated by fitting simulated output to available observational data sets. Simulations showed elevated nutrients and primary production in inshore areas and gulfs that can be linked to point sources of pollution and limited flushing. The model also revealed complex inter-specific relationships among the biological groups. For example, the introduced Nile perch (\emph{Lates niloticus}) exhibited a strong negative correlation with haplochromine cichlids (their prey) as well as most of other fish groups. This brings to fore the significance of predator-prey relationships and the impact of introduced species; information that is critical for effective fisheries and ecosystem management. The model was then used to simulate the impact of different fishing scenarios on the ecosystem. Scenarios tested included varied fishing pressure for Nile perch (the main predator at the top of the food chain), key prey species (haplochromines) and other species. The effects of these scenarios were tested using six common ecosystem-level indicators. Predictions showed that no particular scenario excels in all the six indicators. However, halting harvesting of haplochromines results in the best overall ecosystem performance. This scenario is projected to result in the highest yield of commercially important species and possibly cause minimal disruption to fishing activities. Findings of this study reinforce the need for an ecosystem approach to fisheries management in Lake Victoria.Viktoríuvatn er mikilvægt strandbyggjum sínum, vistfræðilega, félagslega og efnahagslega. Talsvert álag er á vistkerfið sakir ofveiði, innleiðingar framandi tegunda, mengunar og loftlagsbreytinga. Breytingar af þeim sökum, auk flókinnar vistfræði, hafa takmarkað möguleika á skilning á kerfinu sjálfu, helstu ferlum, áhrifavöldum og viðbrögð kerfisins við breytingum. Til að mæta þessari áskorun hefur heildstætt vistkerfislíkan (Atlantis) verið þróað fyrir vatnið. Sérstakt straumalíkan var þróað fyrir vatnið til að setja upp straumkerfi gögn fyrir vistkerfislíkanið. Straumalíkanið var byggt á upplýsingum um dýpi, rennsli áa ásamt upplýsingum um loftþrýsting og úrkomu. Straumkerfislíkanið sýndi hringrás vatns og þróun hitastigs í vatninu. Atlantis líkanið fyrir Viktoríuvatn inniheldur 12 svæði, byggt á líf- og eðlisfræðilegum eiginleikum. Notast var við 38 hópa lífvera og fjóra veiðiflota með ólíkt valmynstur. Líkanið var mátað við ýmis fyrirliggjandi gögn. Útreikningar sýna aukið magn næringarefna og frumframleiðslu, bæði á grunnslóð og dýpi, sem tengist þekktum uppsprettum mengunar og takmörkuðu gegnumstreymi. Í líkaninu komu einnig fram flókin tiltekin tengsl milli líffræðilegra hópa. Þannig sýndi Nílarkarfi sterka neikvæða fylgni við bráð (haplochromines) og raunar flesta hópa fiska. Þetta sýnir vel mikilvægi samspils afræningja og bráða auk áhrifa innfluttra tegunda og nauðsyn þess að líta á allt vistkerfið þegar v stjórna skal veiðum. Líkanið var síðan notað til að prófa áhrif mismunandi veiðistjórnunar á lífríkið. Sviðsmyndir voru m.a. breytilegt veiðiálag á Nílarkarfa (ránfiskur og efstur í fæðukeðjunni), lykilbráð (haplochromines) og aðrar tegundir. Áhrif sviðsmyndanna voru metin með sex algengum mælikvörðum. Niðurstöðurnar bentu ekki til þess að nein stjórnunaraðferðanna bæri af í öllum sex mælikvörðunum. Prófanir sýna hins vegar að sú aðferð að stöðva veiðar á helstu bráð gefi bestan almennan árangur. Hér fæst mestur afli úr efnahagslega mikilvægum stofnum og lágmarks röskun á veiðum. Niðurstöður rannsóknarinnar sýna vel þörfina fyrir vistkerfisnálgun við stjórnun fiskveiða í Viktoríuvatni.United Nation University - Fisheries Training Programm

Modeling of Marine Ecosystems: Experience, Modern Approaches, Directions of Development (Review). Part 1: End-to-End Models

Purpose. Despite of a relatively short history of marine systems modeling, which started in late 1960s – early 1970s, this discipline is developing quite intensively. Publications on marine system modeling number in the thousands. The purpose of the article is to review the achievements accumulated in this field. The main attention is paid to the general principles in marine systems modeling, and to the spectrum of the applied modern approaches. The results of analysis of more than 200 sources, i.e. research papers, monographs, sections in books, internet-resources, are summarized in the paper of two parts published separately. Methods and Results. Over the past decades, our understanding of the patterns of marine ecosystems functioning has increased significantly, as well as the possibilities of ecological monitoring and information technologies. At the same time, the increasing number of global and regional environmental programs and projects in the field of rational use of marine resources, protection of marine ecosystems, and assessment of the climate change impacts has resulted in growth of demands for quantitative tools providing the ecosystem-based support of the initiatives in rational management of sea resources. This, in its turn, has required more complex multi-component models and led to significant increase in the number of such models. The first part of this review is focused on the end-to-end models which represent the complex integrative tools assisting in taking correct decisions for rational management of marine resource. Conclusions. Providing testing of scenarios “what, if”, the end-to-end models are the effective modeling instruments for assessing the consequences of climatic and anthropogenic impacts on all the trophic levels of marine ecosystems including bio-geo-chemical cycle, microbial loop, and various kinds of detritus. These models are not intended for taking tactical decisions (in such cases, local object-oriented sub-models should be used), but they are indispensable instruments in strategic planning and complex assessing of the management strategies

Ocean Futures Under Ocean Acidification, Marine Protection, and Changing Fishing Pressures Explored Using a Worldwide Suite of Ecosystem Models

Ecosystem-based management (EBM) of the ocean considers all impacts on and uses of marine and coastal systems. In recent years, there has been a heightened interest in EBM tools that allow testing of alternative management options and help identify tradeoffs among human uses. End-to-end ecosystem modeling frameworks that consider a wide range of management options are a means to provide integrated solutions to the complex ocean management problems encountered in EBM. Here, we leverage the global advances in ecosystem modeling to explore common opportunities and challenges for ecosystem-based management, including changes in ocean acidification, spatial management, and fishing pressure across eight Atlantis (atlantis.cmar.csiro.au) end-to-end ecosystem models. These models represent marine ecosystems from the tropics to the arctic, varying in size, ecology, and management regimes, using a three-dimensional, spatially-explicit structure parametrized for each system. Results suggest stronger impacts from ocean acidification and marine protected areas than from altering fishing pressure, both in terms of guild-level (i.e., aggregations of similar species or groups) biomass and in terms of indicators of ecological and fishery structure. Effects of ocean acidification were typically negative (reducing biomass), while marine protected areas led to both “winners” and “losers” at the level of particular species (or functional groups). Changing fishing pressure (doubling or halving) had smaller effects on the species guilds or ecosystem indicators than either ocean acidification or marine protected areas. Compensatory effects within guilds led to weaker average effects at the guild level than the species or group level. The impacts and tradeoffs implied by these future scenarios are highly relevant as ocean governance shifts focus from single-sector objectives (e.g., sustainable levels of individual fished stocks) to taking into account competing industrial sectors\u27 objectives (e.g., simultaneous spatial management of energy, shipping, and fishing) while at the same time grappling with compounded impacts of global climate change (e.g., ocean acidification and warming)

Ecosystem modelling in the Eastern Mediterranean Sea : the cumulative impact of alien species, fishing and climate change on the Israeli marine ecosystem

Firstly, I reviewed modelling approaches that were used to assess the impact of invasive alien species (IAS) in aquatic ecosystems. According to the review, multispecies/ecosystem mechanistic models dominated the applications, with dynamic and non-spatial models being the most prevalent. Most of the models included an additional human stressor, mainly fisheries, climate change and/or nutrient loading. I summarised the main features of these applications and analysed their capabilities and limitations. Based on my conclusions, I reflected on future directions of development and applications of suitable modelling tools. The review showed that the Ecopath with Ecosim (EwE) modelling approach was frequently used to assess the impacts of already established IAS and highlighted its capabilities to forecast existing, emerging and potential new IAS. As a second step, I developed two static Ecopath ecosystem models using the EwE approach and representing the food web of the Israeli Mediterranean coast in 1990s and 2010s. I characterized the structure and functioning of the ecosystem and assessed past and current impacts of IAS and fishing. I then used the time-dynamic Ecosim module of EwE to fit the 1990s model to available time series of observations between both periods and to explore the historical dynamics of the ecosystem considering the effects of IAS, fishing dynamics and sea warming. Finally, the time-dynamic ecosystem model was used to analyse alternative future simulations of ecosystem change. Particularly, and after interacting with key stakeholders, I assessed the future effects of a new set of fishing regulations currently being implemented in Israel, future changes in sea temperature following IPCC (Intergovernmental Panel on Climate Change) scenario projections and the potential increases in IAS biomass. I investigated the impacts of the stressors separately, and then I combined them to evaluate their cumulative effects. Results from the static Ecopath models highlighted that the Israeli marine ecosystem, despite productivity differences, shared some structural and functional traits with other Mediterranean ecosystems such as the dominance of the pelagic domain in term of flows, the important role of detritus through low trophic levels and the importance of the benthic-pelagic coupling. In both time periods investigated, the same keystone groups were identified with the exception of European hake in 2010s, which showed a decline in its keystone role. This may indicate that hake lost its ecological role due to population declines. Most of the functional groups identified as keystone species were previously identified as keystones in other Mediterranean ecosystems, such as dolphins, large pelagic fishes, sharks and squids. The temporal dynamic Ecosim model indicated that trophic interactions, ocean warming and fishing were important drivers of the ecosystem dynamics. In general, temporal biomass trends revealed that native demersal predators and native medium trophic level fishes largely declined over time, while an increase over time of alien species was observed. Results from ecological indicators suggested a degradation pattern of the ecosystem over time. Future scenarios using the temporal dynamic Ecosim model showed overall potential benefits of fishing effort reductions in the future, and detrimental impacts of increasing sea temperature and increasing biomass of alien species. Cumulative scenarios highlighted that the beneficial effects of fisheries reduction could be dampened by the impact of increasing sea temperature and alien species when acting together. These results support the need for reducing local and regional stressors, such as fishing and biological invasions, to retain marine ecosystems within a “safe operating space” and ensure ecosystem resilience in an ongoing warming and impacted sea.Los ecosistemas marinos del Mediterráneo oriental han sufrido cambios ecológicos importantes debido a múltiples presiones antropogénicas, incluido el impacto de especies invasoras, la sobrepesca y el calentamiento del mar. En primer lugar, he revisado los modelos que se han utilizado para evaluar el impacto de las especies invasoras en los ecosistemas acuáticos. De acuerdo con esta revisión, predominan los modelos mecanísticos de carácter multiespecífico/ecosistémico, siendo los modelos dinámicos y no espaciales los más frecuentes. La mayoría de los modelos incluyen un impacto antropogénico adicional, principalmente la pesca, el cambio climático y el aporte de nutrientes. Además, he resumido las principales características de estos modelos y he analizado sus capacidades y limitaciones. En base a las conclusiones de esta revisión, se han mostrado posibles direcciones para futuros desarrollos de los modelos y la aplicación de modelos adecuados. En esta revisión, he observado que el modelo Ecopath with Ecosim (EwE) ha sido utilizado frecuentemente para evaluar los impactos de las especies invasoras ya establecidas. Además, la revisión ha destacado las capacidades de EwE de pronosticar los futuros impactos de las especies invasoras establecidas, emergentes y potenciales. Otras revisiones disponibles en la literatura han demostrado las capacidades de EwE para evaluar los impactos de la pesca y el cambio climático. Por lo tanto, he desarrollado dos modelos estáticos Ecopath que representan la red trófica de la costa Mediterránea de Israel en los años 1990 y 2010 para caracterizar la estructura y funcionamiento del ecosistema y evaluar los impactos de las especies invasoras y la pesca en el pasado y en el presente. Después he utilizado el módulo dinámico-temporal Ecosim para ajustar el modelo de 1990 a series temporales de datos disponibles entre ambos periodos y para explorar la dinámica histórica del ecosistema considerando el efecto de las especies invasoras, la dinámica de la flota pesquera y el calentamiento del mar. Finalmente, el módulo dinámico-temporal ha sido utilizado para realizar simulaciones futuras de cambios en el ecosistema. En particular, he evaluado los efectos de un nuevo conjunto de regulaciones de pesca que se están implementando actualmente en Israel, futuros cambios en la temperatura del mar siguiendo las proyecciones del Panel Intergubernamental sobre el Cambio Climático (IPCC por sus siglas en inglés) y posibles aumentos de la biomasa de las especies invasoras. Primero he investigado los diferentes impactos por separado y, luego, los he combinado para evaluar sus efectos acumulativos. Los resultados de los modelos estáticos Ecopath han destacado que el ecosistema marino israelí, a pesar de un patrón de productividad diferente, comparte algunas características estructurales y funcionales con otros ecosistemas mediterráneos como el dominio del hábitat pelágico en términos de flujos tróficos, el importante papel del detritus a través de niveles tróficos bajos y la importancia del acoplamiento bentónicopelágico. Los mismos grupos funcionales clave fueron identificados en ambos periodos investigados, a excepción de la merluza en 2010, lo que puede indicar que la merluza ha perdido su papel ecológico debido al declive de su población. La mayoría de los grupos funcionales identificados como especies clave ya han sido identificados previamente como tales en otros ecosistemas mediterráneos como por ejemplo los delfines, los grandes peces pelágicos, los tiburones y los calamares. El módulo dinámico-temporal Ecosim indicó que las interacciones tróficas, el aumento de la temperatura del mar y la pesca jugaron un papel clave en la dinámica del ecosistema. En general, las tendencias temporales de la biomasa revelaron que los depredadores demersales nativos (por ejemplo, la merluza) y los peces demersal nativos de nivel trófico medio (por ejemplo, los salmonetes) disminuyeron en gran medida con el tiempo, mientras que se observó un aumento de las especies invasoras con el tiempo. Los resultados de los indicadores ecológicos sugirieron un patrón de degradación del ecosistema con el tiempo. Los escenarios futuros utilizando el módulo dinámico-temporal Ecosim mostraron los beneficios potenciales generales de las reducciones del esfuerzo pesquero y los impactos negativos del aumento de la temperatura del mar y el aumento de la biomasa de las especies invasoras. Los escenarios acumulativos resaltaron que los efectos beneficiosos de la reducción de la pesca pueden verse disminuidos por el impacto del aumento de la temperatura del mar y las especies invasoras cuando actúan al mismo tiempo. Estos resultados respaldan la necesidad de reducir los impactos antropogénicos locales y regionales como la pesca y las especies invasoras, para mantener los ecosistemas marinos dentro de un “espacio operativo seguro (SOS por sus siglas en inglés)” y promover la resiliencia de los ecosistemas en un mar en continuo calentamiento y altamente impactado.Els ecosistemes marins de la Mediterrànea oriental han patit canvis ecológics importants a causa de múltiples pressions antropogèniques, inclòs l’impacte d’especies invasores, la sobrepesca i el calentament del mar. En primer lloc, he revisat els models que s’han utilitzat per avaluar l’impacte de les espècies invasores en ecosistemes aquàtics. D’acord amb aquesta revisió, predominen els models mecanístics de caràcter multiespecífic/ecosistèmic, sent els models dinàmics i no espacials els més freqüents. La majoria dels models inclouen un impacte antropogènic adicional, principalment la pesca, el canvi climàtic i l’aport de nutrients. A més, he resumit les principals característiques d’aquest models i he analitzat les seves capacitats i limitacions. En base a les conclusions d’aquesta revisió, s’han exposat possibles direccions per futurs desenvolupaments dels models i l’aplicació de models adecuats. En aquesta revisió he observat que el model Ecopath with Ecosim (EwE) ha estat utilitzat freqüentment per avaluar els impactes de les espècies invasores ja establertes. A més, la revisió ha destacat les capacitats d’EwE de pronosticar els futurs impactes de les espècies establertes, emergents i potencials. Altres revisions disponibles a la literatura han demostrat les capacitats d’EwE per avaluar els impactes de la pesca i el canvi climàtic. Per tant, he desencolupat dos models estàtics Ecopath que representen la xarxa tròfica de la costa Mediterrànea d’Israel en els anys 1990 y 2010 per caracteritzar l’estructura i funcionament de l’ecosistema i avaluar els impactes de les espècies invasores i la pesca en el passat i el present. Després he utilitzat el mòdul dinàmic-temporal per ajustar el model de 1990 a sèries temporals de dades disponibles considerant l’efecte de les espècies invasores, la dinàmica de la flota pesquera i l’escalfament del mar. Finalment, el mòdul dinamic-temporal ha estat utilitzat per realitzar simulacions futures de canvis en l’ecosistema. En particular, he avaluat els efectes d’un nou conjunt de regulacions de pesca que s’estan implementant actualment a Israel, canvis en la temperatura del mar seguint les projeccions del panell intergovernamental sobre el Canvi Climàtic (IPCC per les seves sigles en anglès) i possibles augments de la biomass de les espècies invasores. Primer he investigat els diferents impactes per separat i, després, els he combinat per avaluar els seus efectes acumulatius. Els resultats dels models estàtics Ecopath han destacat que l’ecostema marí d’Israel, malgrat un patró de productivitat diferent, comparteix algunes característiques estructurals i de funcionals amd altres ecosistemes marins mediterrànis com el domini de l’hàbitat pelàgic en termes de fluxes tròfics, l’important paper del detritus a través de nivells tròfics baixos i la importància de l’acoplament bentònic-pelàgic. Els mateixos grups funcionals clau van ser identificats en els dos períodes investigats, a excepció del lluç en el 2010, que pot indicar que el lluç ha perdut el seus paper ecològic a causa del declivi de la seva població. La majoria del grups funcionals identificats com a espècies claus ja han estat identificats com a tals en altres ecosistemes mediterranis com ara els dofins, els gran peixos pelàgics, els taurons i els calamars. El mòdul dinàmic-temporal Ecosim ha indicat que les interaccions tròfiques, l’augment de la temperatura del mar i la pesca van jugar un paper clau en la dinàmic de l’ecosistema. En general, les tendències temporals de la biomasa van revelar que els depredadors demersals natius (per exemple, el lluç) i els peixos dersals natius de nivell tròfic mitjà (per exemple, els rogers) van disminuir en gran mesura amb el temps, mentre que es va observar un augment de les espècies invasores amb el temps. Els resultats dels indicadors ecològics van suggerir un patrò de degradació de l’ecosistema amb el temps. Els escenaris futurs van mostrar els beneficis potencials generals de les reduccions de l’esforç pesquer i els impactes negatius de l’augment de la temperatura del mar i ’augment de la biomasa de les espècies invasores. Els escenaris acumulatius van ressaltar que els efectes beneficiosos de la reducció de la pesca poden ser reduïts per l’impacte de l’augment de la temperatura del mar i les espècies invasores quan actuen al mateix temps. Aquests resultats recolzen la necessitat de reduir els impactes antropogènics locals i regionals com la pesca i les espècies invasores, per mantenir els ecosistems marins dins d’un “espai operatiu segur (SOS per les seves sigles en anglès)” i promoure la resiliència dels ecosistemes en un mar en continu escalfament i altament impactat

Biogas-fuelled aqua-ammonia absorption refrigeration as a means of reducing post-harvest losses in rural Sub-Saharan Africa

Process Engineerin