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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 (NH 4 + ), nitrate + nitrite (NO 3 - ), dissolved inorganic nitrogen (DIN), soluble reactive phosphorus (SRP), total dissolved phosphorus (TDP), and POM stable N isotope (δ 15 N) 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 NH 4 + , SRP, total dissolved nitrogen (TDN), TDP, and sucralose were observed with elevated algal δ 15 N. 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 δ 15 N values, NO 3 - 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., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

In situ measurements were undertaken to characterize particle fields in undisturbed oceanic environments. Simultaneous, co-located depth profiles of particle fields and flow characteristics were recorded using a submersible holographic imaging system and an acoustic Doppler velocimeter, under different flow conditions and varying particle concentration loads, typical of those found in coastal oceans and lakes. Nearly one million particles with major axis lengths ranging from ∼14 μm to 11.6 mm, representing diverse shapes, sizes, and aspect ratios were characterized as part of this study. The particle field consisted of marine snow, detrital matter, and phytoplankton, including colonial diatoms, which sometimes formed "thin layers" of high particle abundance. Clear evidence of preferential alignment of particles was seen at all sampling stations, where the orientation probability density function (PDF) peaked at near horizontal angles and coincided with regions of low velocity shear and weak turbulent dissipation rates. Furthermore, PDF values increased with increasing particle aspect ratios, in excellent agreement with models of spheroidal particle motion in simple shear flows. To the best of our knowledge, although preferential particle orientation in the ocean has been reported in two prior cases, our findings represent the first comprehensive field study examining this phenomenon. Evidence of nonrandom particle alignment in aquatic systems has significant consequences to aquatic optics theory and remote sensing, where perfectly random particle orientation and thus isotropic symmetry in optical parameters is assumed. Ecologically, chain-forming phytoplankton may have evolved to form large aspect ratio chains as a strategy to optimize light harvesting.