Particulate matter concentration (PM, often referred to as total suspended solids [TSS]) is an important parameter in the evaluation of water quality. Several optical measurements used to provide an estimate of water turbidity have also been used to estimate PM, among them light transmission, backscattering, and side-scattering. Here we analyze such measurements performed by the Alliance for Coastal Technologies (ACT) at various coastal locations to establish whether a given optical method performs better than others for the estimation of PM. All the technologies were found to perform well, predicting PM within less than 55% relative difference for 95% of samples (n = 85, four locations). Backscattering performed best as a predictor of PM, predicting PM with less than 37% relative difference for 95% of samples. The correlation coefficient (R) was between 0.96 and 0.98 for all methods with PM data ranging between 1.2 to 82.4 g m -3. In addition, co-located measurements of backscattering and attenuation improves PM prediction and provides compositional information about the suspended particles; when their ratio is high, the bulk particulate matter is dominated by inorganic material while when low, dominated by organic material.

Recurrent blooms of harmful algae and cyanobacteria (HABs) plague many coastal and inland waters throughout the United States and have significant socioeconomic impacts to the adjacent communities. Notable HAB events in recent years continue to underscore the many remaining gaps in knowledge and increased needs for technological advances leading to early detection. This review summarizes the main research and management priorities that can be addressed through ocean observationbased approaches and technological solutions for harmful algal blooms, provides an update to the state of the technology to detect HAB events based on recent activities of the Alliance for Coastal Technologies (ACT), offers considerations for ensuring data quality, and highlights both ongoing challenges and opportunities for solutions in integrating HAB-focused technologies in research and management. Specifically, technological advances are discussed for remote sensing (both multispectral satellite and hyperspectral); deployable in situ detection of HAB species on fixed or mobile platforms (based on bulk or taxa-specific biomass, images, or molecular approaches); and field-based and/or rapid quantitative detection of HAB toxins (via molecular and analytical chemistry methods). Suggestions for addressing challenges to continued development and adoption of new technologies are summarized, based on a consensus-building workshop hosted by ACT, including dealing with the uncertainties in investment for HAB research, monitoring, and management. Challenges associated with choosing appropriate technologies for a given ecosystem and/or management concern are also addressed, and examples of programs that are leveraging and combining complementary approaches are highlighted.

A B S T R A C TThe Alliance for Coastal Technologies (ACT) has been established to support innovation and to provide the information required to select the most appropriate tools for studying and monitoring coastal and ocean environments. ACT is a consortium of nationally prominent ocean science and technology institutions and experts who provide credible performance data of these technologies through third-party, objective testing. ACT technology verifications include laboratory and field tests over short-and long-term deployments of commercial technologies in diverse environments to provide unequivocal, unbiased confirmation that technologies meet key performance requirements. ACT demonstrations of new technologies validate the technology concept and help eliminate performance problems before operational introduction. ACT's most recent demonstration of pCO 2 sensors is an example of how ACT advances the evolution of ocean observing technologies, in this case to address the critical issue of ocean acidification, and promotes more informed decision making on technology capabilities and choices.

Lake Erie's central basin experiences seasonal anoxia, contributing to internal sediment phosphorus (P) loading and exacerbating eutrophication. The precise conditions required for internal loading are poorly understood. This study constrains the timing and rates of internal P loading using continuous in situ temperature, dissolved oxygen (DO), and soluble reactive P (SRP) observations from two sites. SRP concentrations remained low during normoxia (>2 mg of DO L −1 ) and hypoxia (0−2 mg of DO L −1 ) but increased abruptly after anoxia for 12−42 h. SRP flux rate estimations varied, likely due to advection and hypolimnion thickness variation, but could still be reasonably quantified. Flux rates and standard errors during anoxia averaged 25.67 ± 5.5 mg m −2 day −1 at the shallower site and 11.42 ± 2.6 mg m −2 day −1 at the deeper site. At the shallower site, the anoxic hypolimnion was displaced with normoxic water, causing cessation of P flux until anoxia returned, and higher flux rates resumed immediately (89.1 ± 8.6 mg m −2 day −1 ), suggesting rapid, redox-controlled P desorption from surface sediments. On the basis of our rate and onset findings, the expected anoxic area and duration in the basin could yield an annual internal SRP load comparable to the annual central basin TP tributary load of 10000−11000 metric tonnes.