Charting a course for genetic diversity in the UN Decade of Ocean Science

Abstract The health of the world's oceans is intrinsically linked to the biodiversity of the ecosystems they sustain. The importance of protecting and maintaining ocean biodiversity has been affirmed through the setting of the UN Sustainable Development Goal 14 to conserve and sustainably use the ocean for society's continuing needs. The decade beginning 2021–2030 has additionally been declared as the UN Decade of Ocean Science for Sustainable Development. This program aims to maximize the benefits of ocean science to the management, conservation, and sustainable development of the marine environment by facilitating communication and cooperation at the science–policy interface. A central principle of the program is the conservation of species and ecosystem components of biodiversity. However, a significant omission from the draft version of the Decade of Ocean Science Implementation Plan is the acknowledgment of the importance of monitoring and maintaining genetic biodiversity within species. In this paper, we emphasize the importance of genetic diversity to adaptive capacity, evolutionary potential, community function, and resilience within populations, as well as highlighting some of the major threats to genetic diversity in the marine environment from direct human impacts and the effects of global climate change. We then highlight the significance of ocean genetic diversity to a diverse range of socioeconomic factors in the marine environment, including marine industries, welfare and leisure pursuits, coastal communities, and wider society. Genetic biodiversity in the ocean, and its monitoring and maintenance, is then discussed with respect to its integral role in the successful realization of the 2030 vision for the Decade of Ocean Science. Finally, we suggest how ocean genetic diversity might be better integrated into biodiversity management practices through the continued interaction between environmental managers and scientists, as well as through key leverage points in industry requirements for Blue Capital financing and social responsibility.

• The second draft of the UN Decade of Ocean Science Implementation Plan overlooks the importance of genetic diversity in our oceans • Genetic diversity is the basis for adaptation and evolutionary change at species and population levels, and is a key factor influencing the resilience and functionality of marine ecosystems • Genetic diversity will be of key importance for maximising the potential for long term survival of marine populations and species • Genetic diversity is expected to a play a key role in ecosystem resilience and adaptability in the face of climate change as well as supporting the sustainable development of world aquaculture, fisheries, and the Blue Economy • Marine genetic diversity has already been severely impacted by anthropogenic influences, including overexploitation, habitat destruction, species introductions and invasions, and climate change • Despite the importance of genetic diversity for the maintenance of biodiversity, it is still often overlooked in policy and legislation • We believe that the Decade of the Ocean Implementation Plan should explicitly recognise the importance of genetic diversity and ensure that it is taken in to account in the next ten years • To that end, we have made a number of suggested inclusions of genetic diversity, notably in Decade Outcome 2, Decade Outcome 3 and Decade Challenge 2 • Ultimately, the inclusion of genetic diversity will facilitate and support the maintenance of genetic biodiversity in the coming decade, and in doing so, support ecosystem resilience and adaptability in the face of climate change alongside the sustainable development of our oceans.
The Significance of Genetic Diversity A significant omission from the second draft of the UN Decade of Ocean Science Implementation plan is the acknowledgement of intraspecific genetic diversity in relation to marine biodiversity and sustainable development 1 . Genetic diversity represents one of the three fundamental pillars of biodiversity alongside interspecies diversity and ecosystem diversity. Genetic diversity is the basis for adaptation and evolutionary change at species and population levels, and underpins the resilience and functionality of marine ecosystems 2,3 . At a community level, genetic diversity has been found to have a role in ecosystem productivity, stability, and function comparable to that of interspecific diversity [4][5][6] . Furthermore, changes in intraspecific genetic diversity can have intergenerational effects at population, species, and community scales and significant knock-on effects throughout trophic networks 7,8 . At an evolutionary scale, genetic diversity offers the basic units for adaptive changes that enable species to respond to changes in their environment 9,10 . Evidence suggests that adaptation is often derived from standing genetic variation in local populations and the exchange of genetic variants among populations spanning environmental gradients 11,12 . The central role of genetic diversity in adaptation and ecosystem resilience is therefore likely to be of vital importance in the face of anthropogenic climate change [13][14][15] . Consequently, the conservation and maintenance of genetic diversity must be a management priority for ensuring the future resilience of marine ecosystems.
Despite its importance, genetic diversity in many wild populations has significantly declined since the industrial revolution, largely driven by anthropogenic impacts including overharvesting, habitat loss and fragmentation, genetic introgression from invasive and domesticated species, and climate change [16][17][18][19] . Impacts from these can often have delayed or cryptic effects which can be easily overlooked 20,21 . Losses of genetic diversity can also take significantly longer to recover than population sizes and distribution thus leaving long lasting effects on population resilience and function 22 .
In the marine environment, anthropogenic impacts have affected genetic diversity of wild populations in numerous ways. Overharvesting has led to fisheries-induced evolutionary effects, whilst pollution and habitat loss have led to losses of genetic diversity in key primary producers and foundation species [23][24][25][26] . Unprecedented rates of marine introductions and pest invasions, alongside accidental and deliberate releases from hatchery environments, have also been a major contributor to genetic diversity loss in native biota due to competition, predation, infection, or introgression effects [27][28][29][30] . The effects of climate change have also been felt more keenly in the marine environment, and genetic losses due to marine heatwaves, range shifts, and population losses are expected to increase in the next ten years if not addressed 20,31-33 . Aside from compromising environmental values, losses of genetic diversity in our seas and oceans also impact important socio-economic and cultural values. The importance of genetic diversity in fisheries, aquaculture, biotechnology and the Blue Economy is highly relevant to the coming Decade of Ocean Science and is intrinsically linked to intraspecific genetic diversity in wild populations [34][35][36] .
Global recognition of the significance of genetic diversity to ecosystem functionality, resilience, and evolutionary potential is increasing. The recent post-2020 draft of the Convention of Biological Diversity highlights the critical role of intraspecific diversity, though early versions required major revisions to address weaknesses in initial diversity targets and indicators 37,38 . Numerous international agreements and reports have acknowledged the importance of genetic diversity in ecosystem function and resilience as well as in sustainable food and aquaculture production. These include Target

Genetic Diversity in the Decade of Ocean Science Implementation Plan
The Decade of Ocean Science Implementation Plan includes an overview of the major threats and impacts to the world's oceans. Yet the document does not explicitly highlight the significance of and threats to marine genetic diversity. The importance of the maintenance of biodiversity is acknowledged, however, failing to differentiate between genetic and species diversity has commonly led to genetic diversity being overlooked in policy and governance 38,42 . We believe that the Implementation Plan should explicitly include the maintenance of both genetic diversity and species diversity in its scope for biodiversity. Specifically, Paragraph 2, which describes the current status and threats to the world's oceans, should explicitly acknowledge the loss of genetic diversity and the threat that this poses to the maintenance of biodiversity. For example, including: "…continued warming on this scale is projected to lead to large-scale disappearance of corals and other highly productive ecosystems that are a cornerstone of the world's biodiversity, and a source of food and livelihoods for hundreds of millions of people. 16 . Deoxygenation resulting from the combined effects of increased nutrient loads and ocean warming is creating 'dead zones' and low oxygen zones throughout the ocean." Secondly, we feel strongly that "the ocean we want" should include genetically diverse and resilient populations, as well as a rich diversity of species and ecosystems. This should be reflected in the Decade Outcomes, in particular Outcome 2 which relates to the health of the ocean's ecosystems, but also in Outcome 3 which aims for "A productive ocean supporting sustainable food supply and a sustainable ocean economy", both of which are intrinsically supported by genetic diversity. To this aim we suggest that the following amendments be made to Outcomes 2 and 3: "Outcome 2: A healthy and resilient ocean where marine ecosystems are understood, protected, restored and managed. Degradation of marine ecosystems is accelerating due to unsustainable activities on land and in the ocean. To sustainably manage, protect or restore marine and coastal ecosystems, priority knowledge gaps of ecosystems, and their reactions to multiple stressors, need to be filled.

The maintenance of genetic and species biodiversity should also be considered a central component in maintaining resilience and adaptive capacity in marine ecosystems.
This is particularly true where multiple human stressors interact with climate change, including acidification and temperature increase. Such knowledge is important to develop tools to implement management frameworks that build resilience, recognise thresholds and avoid ecological tipping points, and thus ensure ecosystem functioning and continued delivery of ecosystem services for the health and wellbeing of society and the planet as a whole." "Outcome 3: A productive ocean supporting sustainable food supply and a sustainable ocean economy. The ocean is the foundation for future global economic development and human health and wellbeing, including food security and secure livelihoods for hundreds of millions of the world's poorest people. Knowledge and tools to support the recovery of wild fish stocks, deploy sustainable fisheries management practices, and support the sustainable expansion of aquaculture, while protecting and maintaining essential genetic and interspecific biodiversity within ecosystems, will be essential. The ocean also provides essential goods and services to a wide range of established and emerging industries including extractive industries, energy, tourism, transport and pharmaceutical industries. Each of these sectors has specific, priority needs in terms of increased knowledge, and support to innovation, technological development and decision support tools to minimise risk, avoid lasting harm, and optimise their contribution to the development of a sustainable ocean economy. Governments also require information and tools, for example via national accounts that incorporate ocean indicators, to guide development of sustainable ocean economies and promote marine sectors.

Proposed indicators at all levels of biodiversity, including genetic diversity, should also be implemented."
Finally, these aims should be incorporated into the Action Framework and relevant Ocean Decade Challenges to ensure that these are translated into meaningful actions. Differentiating between genetic and species biodiversity in Ocean Decade Challenge 2 in particular would ensure that genetic diversity over the next decade would not be overlooked in the sustainable development, management and conservation of our oceans: "Challenge 2: Understand the effects of multiple stressors on ocean ecosystems, and develop solutions to monitor, protect, manage and restore ecosystems and their genetic and species biodiversity under changing environmental, social and climate conditions."

Conclusions
The importance of genetic diversity in maintaining ecosystem function and evolutionary potential cannot be overstated. By explicitly recognising and including genetic diversity in its target Outcomes and Challenges, the Decade of Ocean Science framework can ensure that genetic diversity is considered in biodiversity assessments in the next ten years of ocean research, development and management. The visibility and reach of the Decade Implementation plan, to governmental, legislative, NGO, and stakeholder groups, will help raise awareness and increase familiarity with the significance of genetic diversity for biodiversity maintenance and sustainable development. The acknowledgement of the importance of genetic diversity in the Implementation Plan can act as the platform from which further actions can be developed and implemented, be they research, management and conservation plans, or further outreach and dissemination. Ultimately, the inclusion of genetic diversity in the Decade of Ocean Science's Challenges and Outcomes will facilitate and support the maintenance of genetic biodiversity in the coming decade. In doing so, the Decade of Ocean Science will further achieve its core goal of supporting ecosystem resilience and adaptability in the face of climate change alongside the sustainable development of the ocean for our continuing needs.