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The concept of nonlinear, sudden responses of ecosystems or species to environmental change has engendered significant interest in the past two decades. Many reviews and theoretical papers have addressed alternative states or stable states, regime shifts, tipping points and phase shifts, but the empirical evidence for these phenomena, which we refer to as stark changes, has not been evaluated in estuaries and nearshore marine ecosystems. We developed standard definitions for these phenomena and examined the functional forms of ecological responses to environmental pressures (i.e. proximate influences on ecosystem state). We searched for publications related to estuaries and nearshore marine ecosystems that included common descriptors of stark change in their keywords. Our search yielded 376 papers, of which we retained 98 that met four criteria: (1) claimed a stepped biological change; (2) inferred change from empirical data; (3) addressed changes that occurred in one or more semi-enclosed, tidally influenced ecosystems; and (4) described a connection to long-term patterns of ecological change. Although there were many instances of changes in ecological states, most were not stark changes. Evidence generally was not derived from time-series data, and many studies inferred temporal change from spatial differences. We describe the eight studies that provided some evidence of stark changes in ecosystem state. We suggest that compelling evidence of stark changes that can be related to pressures requires concurrent time-series data on the ecological response and pressures that were claimed to induce the stark changes. [ABSTRACT FROM AUTHOR]