Data_Sheet_1_A Macroalgal Cultivation Modeling System (MACMODS): Evaluating the Role of Physical-Biological Coupling on Nutrients and Farm Yield.pdf

Offshore aquaculture has the potential to expand the macroalgal industry. However, moving into deeper waters requires suspended structures that will present novel farm-environment interactions. Here, we present a computational modeling framework, the Macroalgal Cultivation Modeling System (MACMODS), to explore within-farm modifications to light, seawater flow, and nutrient fields across time and space scales relevant to macroalgae. A regional ocean model informs the site-specific setting, the Santa Barbara Channel in the Southern California Bight. A fine-scale hydrodynamic model predicts modified flows and turbulent mixing within the farm. A spatially resolved macroalgal growth model, parameterized for giant kelp, Macrocystis pyrifera, predicts kelp biomass. Key findings from model integration are that regional ocean conditions set overall farm performance, while fine-scale within-farm circulation and nutrient delivery are important to resolve variation in within-farm macroalgal performance. Therefore, we conclude that models resolving within-farm dynamics can provide benefit to farmers with insight on how farm design and regional ocean conditions interact to influence overall yield. Here, the presence of repeating longlines aligned with the mean current generate flow diversions around the farm as well as attached Langmuir circulations and increased turbulence intensity. These flow-induced phenomena lead to less biomass in the interior portion of the farm relative to the edges. We also find that there is an effluent “footprint” that extends as much as 20 km beyond the farm. In this regard, MACMODS can be used to not only evaluate farm design and cultivation practices that maximize yield but also explore interactions between the farm and ecosystem in order to minimize impacts.

近海养殖具备拓展大型藻类产业的潜力。然而，向更深水域拓展养殖则需采用悬浮养殖结构，这将带来全新的养殖设施与环境的相互作用。本研究提出一款计算建模框架——大型藻类养殖建模系统（Macroalgal Cultivation Modeling System，MACMODS），用于探究与大型藻类生长相关的时空尺度下，养殖区内光照、海水流场及营养盐场的内部变化规律。该框架以区域海洋模型为基础，适配南加州湾圣巴巴拉海峡的特定场地条件；高精度水动力模型可预测养殖区内经改造的流场与湍流混合过程；以巨藻（Macrocystis pyrifera）为参数化对象的空间解析型大型藻类生长模型，可预测巨藻生物量。模型整合后的关键研究结果表明：区域海洋条件决定了养殖整体的生产效能，而养殖区内的精细尺度环流与营养盐输送过程，对于解析大型藻类在养殖区内的生产效能差异至关重要。因此本研究认为，能够解析养殖区内动态过程的模型，可为养殖从业者提供关于养殖设施设计与区域海洋条件如何相互作用以影响整体养殖产量的参考依据。本研究中，与平均流向对齐的重复布设延绳养殖装置，会在养殖区周围产生流场偏转，同时附带生成兰姆米尔环流（Langmuir circulations）并提升湍流强度。这类流场诱导产生的现象，会导致养殖区内部的生物量低于边缘区域。此外本研究还发现，养殖尾水会形成最远延伸至养殖区外20公里的"足迹"。基于此，大型藻类养殖建模系统（MACMODS）不仅可用于评估可实现产量最大化的养殖设施设计与养殖模式，还可用于探究养殖设施与生态系统之间的相互作用，从而尽可能降低养殖活动对生态环境的负面影响。