Bren School of Environmental Science and Management, University of California, Santa Barbara, CA 93106-5131, USA.
Pacific Biosciences Research Center, Kewalo Marine Laboratory, University of Hawai'i at Mānoa, Honolulu, HI 96813, USA.
Sci Total Environ. 2021 Sep 1;785:146859. doi: 10.1016/j.scitotenv.2021.146859. Epub 2021 Apr 20.
Integrated agriculture and aquaculture systems (IAAS) allow nutrients, energy, and water to flow throughout the components of the system, increasing the efficiency with which inputs are converted to food. Yet effectively designing an IAAS requires understanding how nutrients accumulate and alter the system's productivity. Here we developed a mechanistic model for nitrogen transport and utilization and parameterized it using the IAAS in He'eia, Hawai'i. Of note, we modeled tidal influence, which extends existing IAAS models that often assume aquaculture in tank enclosures. We simulated the impact of nitrogen loading from three possible land use scenarios across agriculture and development priorities on the productivity of the fishpond downstream. We projected that organic nitrogen and nitrate concentrations parallel the successive increases in nitrogen loading across management strategies. Autotroph and fish densities were predicted to follow similar trends in response to increased nitrogen availability, causing fish harvests to increase from the current land use (25 kg/ha) to the restored agriculture (35 kg/ha) and urban (50 kg/ha) alternatives. While fish harvests were predicted to be highest in the urban scenario, modeled caloric production in the restored scenario from agriculture and aquaculture would sustain 235 people (4.3 people/ha) in the He'eia IAAS, 16 and 125 times more than the current or urban land uses, respectively. Restoring diversified agriculture was also predicted to retain a larger proportion of nitrogen inputs (0.43) than urbanizing the region (0.30), which would reduce nitrogen export to the adjacent Kāne'ohe Bay. Several state variables were notably sensitive to tidal flux rates, highlighting the importance of incorporating tidal dynamics into a coastal IAAS model. This model provides valuable insights for the management of existing coastal IAAS and design of new IAAS in coastal regions to improve the sustainability of future food systems.
综合农业和水产养殖系统（IAAS）允许养分、能量和水在系统的各个组成部分中流动，从而提高输入转化为食物的效率。然而，要有效地设计一个 IAAS，需要了解养分是如何积累并改变系统的生产力的。在这里，我们开发了一个氮运输和利用的机制模型，并使用夏威夷 He'eia 的 IAAS 对其进行了参数化。值得注意的是，我们模拟了潮汐的影响，这扩展了现有的 IAAS 模型，这些模型通常假设水产养殖在水箱围场中进行。我们模拟了三种可能的土地利用情景下氮负荷对下游鱼塘生产力的影响，这些情景涉及农业和发展重点。我们预计，有机氮和硝酸盐浓度将与管理策略中氮负荷的连续增加平行。由于氮可用性的增加，自养生物和鱼类的密度预计会出现类似的趋势，从而导致鱼类收获从当前土地利用（25 公斤/公顷）增加到恢复农业（35 公斤/公顷）和城市（50 公斤/公顷）的替代方案。虽然城市情景下的鱼类收获预计最高，但从农业和水产养殖恢复的情景中模拟的热量生产将维持 He'eia IAAS 中的 235 人（4.3 人/公顷），分别是当前或城市土地利用的 16 倍和 125 倍。恢复多样化农业也预计将保留更多的氮输入（0.43），而不是城市化该地区（0.30），这将减少向相邻的 Kāne'ohe 湾的氮输出。几个状态变量对潮流通量率非常敏感，这突出了将潮汐动力学纳入沿海 IAAS 模型的重要性。该模型为现有沿海 IAAS 的管理和沿海地区新的 IAAS 的设计提供了有价值的见解，以提高未来粮食系统的可持续性。
